diff --git a/required/latex-lab/latex-lab-mathcapture.dtx b/required/latex-lab/latex-lab-mathcapture.dtx
deleted file mode 100644
index 84c380996..000000000
--- a/required/latex-lab/latex-lab-mathcapture.dtx
+++ /dev/null
@@ -1,1155 +0,0 @@
-% \iffalse meta-comment
-%
-%% File: latex-lab-mathtagging.dtx
-%
-% Copyright (C) 2022-2023 The LaTeX Project
-%
-% It may be distributed and/or modified under the conditions of the
-% LaTeX Project Public License (LPPL), either version 1.3c of this
-% license or (at your option) any later version.  The latest version
-% of this license is in the file
-%
-%    https://www.latex-project.org/lppl.txt
-%
-%
-% The development version of the bundle can be found below
-%
-%    https://github.com/latex3/latex2e/required/latex-lab
-%
-% for those people who are interested or want to report an issue.
-%
-%<*driver>
-\documentclass{l3doc}
-\EnableCrossrefs
-\CodelineIndex
-
-\usepackage{todonotes}
-
-\begin{document}
-  \DocInput{latex-lab-mathtagging.dtx}
-\end{document}
-%</driver>
-%
-% \fi
-%
-%
-% \title{The \texttt{latex-lab-mathtagging} code\thanks{}}
-% \author{Frank Mittelbach, Joseph Wright, \LaTeX{} Project}
-%
-% \maketitle
-%
-% \newcommand\NEW[1]{\marginpar{\mbox{}\hfill\fbox{New: #1}}}
-% \providecommand\class[1]{\texttt{#1.cls}}
-% \providecommand\pkg[1]{\texttt{#1}}
-% \providecommand\hook[1]{\texttt{#1}}
-%
-% ^^A \car {...} for marginal comments
-% ^^A \car*{...} for longer inline comments
-%
-% \NewDocumentCommand\car{sO{}m}
-%   {\IfBooleanTF{#1}{\todo[inline,color=blue!10,#2]{#3}}^^A
-%                    {\todo[color=blue!10,#2]{#3}}}
-%
-% \NewDocumentCommand\fmi{sO{}m}
-%   {\IfBooleanTF{#1}{\todo[inline,#2]{#3}}^^A
-%                    {\todo[#2]{#3}}}
-%
-%
-%
-% \begin{abstract}
-% \end{abstract}
-%
-% \tableofcontents
-%
-% \section{Introduction}
-%
-% This file implements capture of all math mode material at the outer
-% level, i.e., a formula is captured in its entirety with inner text
-% blocks (possibly containing further math) absorbed as part of the
-% formula. For example,
-%\begin{verbatim}
-%      \[ a \in A \text{ for all $a<5$}  \]
-%\end{verbatim}
-% would only result in a single capture of the tokens
-% ``\verb*/a \in A \text{ for all $a<5$}/''.
-%
-% \subsection{Code level interfaces}
-%
-% \begin{function}{\math_register_env:n, \math_register_env:nn}
-%   \begin{syntax}
-%     \cs{math_register_env:n} \Arg{env}
-%     \cs{math_register_env:nn} \Arg{env} \Arg{options}
-%   \end{syntax}
-%   Registers the \meta{env} as a math environment which should be captured
-%   and made available. This is necessary for all top-level math mode
-%   environments: low-level errors may result if these are not correct
-%   set up. One or more key--value \meta{options} may also be given:
-%   \begin{itemize}
-%     \item[\texttt{arg-spec}] The argument specification taken by the
-%       beginning of the environment; this is used to remove non-mathematical
-%       material.
-%   \end{itemize}
-% \end{function}
-%
-% \begin{function}{\math_processor:n}
-%   \begin{syntax}
-%     \cs{math_processor:n} \Arg{tokens}
-%   \end{syntax}
-%   Declares that the captured math content should be passed to the
-%   \meta{tokens}, which will receive the environment type as |#1| and
-%   the content as |#2|.
-% \end{function}
-%
-% \subsection{Document level interfaces}
-%
-% \begin{function}{\RegisterMathEnvironment}
-%   \begin{syntax}
-%     \cs{RegisterMathEnvironment} \oarg{options} \Arg{env}
-%   \end{syntax}
-%   Registers the \meta{env} as a math environment which should be captured
-%   and made available. This is necessary for all top-level math mode
-%   environments: low-level errors may result if these are not correct
-%   set up. One or more key--value \meta{options} may also be given:
-%   \begin{itemize}
-%     \item[\texttt{arg-spec}] The argument specification taken by the
-%       beginning of the environment; this is used to remove non-mathematical
-%       material.
-%   \end{itemize}
-% \end{function}
-%
-% \MaybeStop{\setlength\IndexMin{200pt}  \PrintIndex  }
-%
-% \section{The Implementation}
-%
-%    \begin{macrocode}
-%<@@=math>
-%    \end{macrocode}
-%
-%    \begin{macrocode}
-%<*kernel>
-%    \end{macrocode}
-%
-% \subsection{File declaration}
-%    \begin{macrocode}
-\ProvidesFile{latex-lab-mathtagging.ltx}
-        [2023-02-06 v0.5a Grab all the math(s) and tag it (experiments)]
-%    \end{macrocode}
-%
-%    \begin{macrocode}
-\AddToHook{begindocument/before}{\RequirePackage{l3lists2}}
-%    \end{macrocode}
-%
-%    \begin{macrocode}
-\ExplSyntaxOn
-%    \end{macrocode}
-%
-% \subsection{Setup}
-%
-% Loading \pkg{amsmath} is an absolute requirement: this avoids needing to
-% have conditional definitions and deals with how to define \cs{[}/\cs{]}
-% neatly.
-%    \begin{macrocode}
-\tl_gput_right:Nn \@kernel@before@begindocument
-  { \RequirePackage { amsmath } }
-%    \end{macrocode} 
-%
-% \subsection{Data structures}
-%
-% \begin{variable}{\l_@@_collected_bool}
-%   Tracks if math mode material has been collected, which happens inside
-%   \pkg{amsmath} environments as well as those handled directly here.
-%    \begin{macrocode}
-\bool_new:N \l_@@_collected_bool
-%    \end{macrocode}
-% \end{variable}
-%
-% \begin{variable}{\g_@@_grabbed_env_tl, \g_@@_grabbed_math_tl}
-%    \begin{macrocode}
-\tl_new:N \g_@@_grabbed_env_tl
-\tl_new:N \g_@@_grabbed_math_tl
-%    \end{macrocode}
-% \end{variable}
-%
-% \subsection{Interface commands}
-%
-% \begin{macro}
-%   {\@@_process:nn, \@@_process:Vn, \@@_process_auxi:nn, \@@_process_auxii:nn}
-%   A no-op place-holder; the internal wrapper means that it does not need to
-%   be concerned with internals.
-%    \begin{macrocode}
-\cs_new_protected:Npn \@@_process:nn #1#2
-  {
-    \legacy_if:nF { measuring@ }
-      {
-        \tl_if_in:nnF {#2} { \m@th }
-          { \tl_trim_spaces_apply:nN {#2} \@@_process_auxi:nn {#1} }
-      }
-  }
-\cs_generate_variant:Nn \@@_process:nn { V }
-\cs_new_protected:Npn \@@_process_auxi:nn #1#2
-  {
-    \tl_gset:Nn \g_@@_grabbed_env_tl {#2}
-    \tl_gset:Nn \g_@@_grabbed_math_tl {#1}
-    \@@_process_auxii:nn {#2} {#1}
-  }
-\cs_new_protected:Npn \@@_process_auxii:nn #1#2 { }
-%    \end{macrocode}
-% \end{macro}
-%
-% \begin{macro}{\math_processor:n}
-%   A simple installer
-%    \begin{macrocode}
-\cs_new_protected:Npn \math_processor:n #1
-  { \cs_set_protected:Npn \@@_process_auxii:nn ##1##2 {#1} }
-%    \end{macrocode}
-% \end{macro}
-%
-% \subsection{Content grabbing}
-%
-% \begin{macro}{\@@_grab_dollar:w}
-%   Grab up to a single |$|, for inline math mode, suppressing
-%   any processing if the first token is \tn{m@th}.
-%    \begin{macrocode}
-\cs_new_protected:Npn \@@_grab_dollar:w % $
-  #1 $
-  {
-%    \end{macrocode}
-%    \fmi{what's that test doing?}
-%    \begin{macrocode}
-    \tl_if_blank:nF {#1}
-      {
-        \@@_process:nn { math } {#1} % $
-% fairly simple this one
-        \tagmcend %end P-chunk, in code: \tag_mc_end_push:
-        \@kernel@math@begin
-        #1 $
-        \@kernel@math@end
-        \tagmcbegin{}  % restart P-chunk (whatsits in pdftex)
-      }
-  }
-%    \end{macrocode}
-% \end{macro}
-% \begin{macro}{\@@_grab_dollardollar:w}
-%   And for the classical \TeX{} display structure.
-%    \begin{macrocode}
-
-\skip_new:N \l_@@_tmpa_skip
-  
-\cs_new_protected:Npn \@@_grab_dollardollar:w % $$
-  #1 $$
-  {
-    \tl_if_blank:nF {#1}
-      {
-        \@@_tag_dollardollar_display:nn { equation* }{#1}
-        #1
-        $$
-      }
-  }
-
-\cs_new_protected:Npn \@kernel@close@P {
-  \tagmcend %end P-chunk, in code: \tag_mc_end_push:
-        \int_gincr:N \g__tag_para_end_int
-        \bool_if:NT \l__tag_para_show_bool
-          { \tag_mc_begin:n{artifact}
-            \rlap{\color_select:n{red}\tiny\ \int_use:N\g__tag_para_end_int}
-            \tag_mc_end:
-          }
-        \tag_struct_end:
-}
-  
-
-
-\cs_new_protected:Npn \@@_tag_dollardollar_display:nn #1#2 {
-  \@@_process:nn {#1} {#2}
-  \@kernel@close@P
-  \@kernel@math@begin
-%        \skip_set:Nn \belowdisplayskip      {-\belowdisplayskip}
-%        \skip_set:Nn \belowdisplayshortskip {-\belowdisplayshortskip}
-%        \int_set:Nn \postdisplaypenalty {10000}
-%%
-%        \group_insert_after:N \@@_tag_dollardollar_display_end:
-}
-
-\cs_new_protected:Npn \@@_tag_dollardollar_display_end: {
-%  \typeout{== tag dollarldollar display end}
-%  \ShowTagging{struct-stack}
-  \tagpdfparaOff
-  \para_raw_end:
-  \tagpdfparaOn
-  \l_@@_tmpa_skip \lastskip  
-  \@kernel@math@end
-  \penalty \postdisplaypenalty
-  \skip_vertical:n { -\l_@@_tmpa_skip }
-%
-  \@doendpe             % this has no \end{...} to take care of it
-}
-
-
-%    \end{macrocode}
-% \end{macro}
-%
-% \begin{macro}{\@@_grab_inline:w}
-%   Collect inline math content and deal with the need to move to math mode.
-%    \begin{macrocode}
-\cs_new_protected:Npn \@@_grab_inline:w % \(
-  #1 \)
-  {
-    \tl_if_blank:nF {#1}
-      {
-        \@@_process:nn { math } {#1}
-        $ #1 $
-      }
-    \bool_set_false:N \l_@@_collected_bool
-  }
-%    \end{macrocode}
-% \end{macro}
-% \begin{macro}{\@@_grab_eqn:w}
-%   For the most common use of \cs{[}/\cs{]}: turn into an environment.
-%    \begin{macrocode}
-\cs_new_protected:Npn \@@_grab_eqn:w % \[
-  #1 \]
-   {
-%     \typeout{collected? = \bool_if:NTF \l_@@_collected_bool {true}{false}}
-     \begin { equation* } #1 \end { equation* }
-   }
-%    \end{macrocode}
-% \end{macro}
-%
-% \subsection{Marking math environments}
-%
-% A general mechanism for math mode environments that do not grab their
-% content (\emph{cf.}~most \pkg{amsmath} environments).
-%
-% \begin{variable}{\l_@@_env_name_tl}
-%  To allow us to carry out \enquote{special effects}
-%    \begin{macrocode}
-\tl_new:N \l_@@_env_name_tl
-%    \end{macrocode}
-% \end{variable}
-%
-% Here we set up specialised handling of environments. The idea for the
-% \texttt{arg-spec} key is that if an environment takes arguments, we
-% don't worry during the main grabbing. Rather, we remove the arguments
-% from the grabbed content and forward only the payload. That is done by
-% (ab)using \pkg{ltcmd}.
-%    \begin{macrocode}
-\keys_define:nn { @@ }
-  {
-     arg-spec .code:n =
-       {
-         \ExpandArgs { c } \DeclareDocumentCommand
-           { @@_env \l_@@_env_name_tl _aux: }
-           {#1}
-           { \@@_env_forward:w }
-       }
-  }
-%    \end{macrocode}
-%
-% \begin{macro}{\math_register_env:nn}
-% \begin{macro}{\math_register_env:n}
-% \begin{macro}{\RegisterMathEnvironment}
-%   Set up to capture environment content and make available.
-%    \begin{macrocode}
-
-\cs_new_protected:Npn \math_register_env:nn #1#2
-  {
-    \tl_set:Nn \l_@@_env_name_tl {#1}
-    \keys_set:nn { @@ } {#2}
-    \cs_gset_eq:cc { @@_env_ #1 _begin: } {#1}
-    \cs_gset_eq:cc { @@_env_ #1 _end: } { end #1 }
-%
-    \ExpandArgs { nnx } \RenewDocumentEnvironment {#1} { b }
-      {
-%        \bool_set_true:N \exp_not:N \l_@@_collected_bool
-%        \cs_if_exist:cTF { @@_env #1 _aux: }
-%          {
-%            \exp_not:c { @@_env #1 _aux: }
-%              ####1 \exp_not:N \@@_env_end: {#1}
-%          }
-%          { \exp_not:N \@@_process:nn {#1} {####1} }
-        \exp_not:N \bool_if:NTF \exp_not:N \l_@@_collected_bool
-          {
-%            \typeout{===>B1}
-          }
-          {
-%            \typeout{===>B2}
-            \cs_if_exist:cTF { @@_env #1 _aux: }
-              {
-                \exp_not:c { @@_env #1 _aux: }
-                  ####1 \exp_not:N \@@_env_end: {#1}
-              }
-              { \exp_not:N \@@_process:nn {#1} {####1} }
-            \exp_not:n { \@kernel@math@registered@begin }
-            \bool_set_true:N \exp_not:N \l_@@_collected_bool
-          }
-%        \exp_not:N \tracingall  
-        \exp_not:c { @@_env_ #1 _begin: }
-        ####1
-        \exp_not:c { @@_env_ #1 _end: }
-%        \exp_not:c { @@_env_ #1 _end: }
-%        \exp_not:N \tracingnone
-%        \exp_not:n { \@kernel@math@registered@end }
-     }
-      {
-      }
-  }
-
-\cs_set_protected:Npn \__cs_tmp:w #1
-  {
-    \group_begin:
-      \exp_args:No \__cs_generate_internal_variant:n
-        { \tl_to_str:n {#1} }
-    \group_end:
-  }
-\__cs_tmp:w { nnxx }
-  
-  
-\cs_new_protected:Npn \math_register_halign_env:nn #1#2
-  {
-    \tl_set:Nn \l_@@_env_name_tl {#1}
-    \keys_set:nn { @@ } {#2}
-    \cs_gset_eq:cc { @@_env_ #1 _begin: } {#1}
-    \cs_gset_eq:cc { @@_env_ #1 _end: } { end #1 }
-%
-    \ExpandArgs { nnxx } \RenewDocumentEnvironment {#1} { b }
-      {
-%        \bool_set_true:N \exp_not:N \l_@@_collected_bool
-%        \cs_if_exist:cTF { @@_env #1 _aux: }
-%          {
-%            \exp_not:c { @@_env #1 _aux: }
-%              ####1 \exp_not:N \@@_env_end: {#1}
-%          }
-%          { \exp_not:N \@@_process:nn {#1} {####1} }
-        \exp_not:N \bool_if:NTF \exp_not:N \l_@@_collected_bool
-          {
-%            \typeout{===>B1}
-          }
-          {
-%            \typeout{===>B2}
-            \cs_if_exist:cTF { @@_env #1 _aux: }
-              {
-                \exp_not:c { @@_env #1 _aux: }
-                  ####1 \exp_not:N \@@_env_end: {#1}
-              }
-              { \exp_not:N \@@_process:nn {#1} {####1} }
-            \exp_not:n { \@kernel@math@registered@begin }
-            \bool_set_true:N \exp_not:N \l_@@_collected_bool
-          }
-%        \exp_not:N \tracingall  
-        \exp_not:c { @@_env_ #1 _begin: }
-        ####1
-%        \exp_not:c { @@_env_ #1 _end: }
-%        \exp_not:N \tracingnone
-     }
-      {
-        \exp_not:c { @@_env_ #1 _end: }
-      }
-  }
-
-\cs_new_protected:Npn \math_register_odd_env:nn #1#2
-  {
-    \tl_set:Nn \l_@@_env_name_tl {#1}
-    \keys_set:nn { @@ } {#2}
-    \cs_gset_eq:cc { @@_env_ #1 _begin: } {#1}
-    \cs_gset_eq:cc { @@_env_ #1 _end: } { end #1 }
-%
-    \ExpandArgs { nnxx } \RenewDocumentEnvironment {#1} { b }
-      {
-        \exp_not:N \bool_if:NTF \exp_not:N \l_@@_collected_bool
-          {
-%            \typeout{===>B1}
-          }
-          {
-%            \typeout{===>B2}
-            \cs_if_exist:cTF { @@_env #1 _aux: }
-              {
-                \exp_not:c { @@_env #1 _aux: }
-                  ####1 \exp_not:N \@@_env_end: {#1}
-              }
-              { \exp_not:N \@@_process:nn {#1} {####1} }
-            \exp_not:n { \@kernel@math@registered@begin }
-            \bool_set_true:N \exp_not:N \l_@@_collected_bool
-          }
-%        \exp_not:N \tracingall  
-        \exp_not:c { @@_env_ #1 _begin: }
-        ####1
-     }
-      {
-        \exp_not:c { @@_env_ #1 _end: }
-% needed if we don't have $$...$$        
-%        \exp_not:n { \typeout{---> @kernel@math@registered@end }}
-        \exp_not:n { \@kernel@math@registered@end }
-      }
-  }
-
-
-
-  \DeclareRobustCommand*\begin[1]{%
-  \UseHook{env/#1/before}%
-  \@ifundefined{#1}%
-    {\def\reserved@a{\@latex@error{Environment #1 undefined}\@eha}}%
-    {\def\reserved@a{\def\@currenvir{#1}%
-        \edef\@currenvline{\on@line}%
-        \@execute@begin@hook{#1}%
-        \csname #1\endcsname}}%
-  \@ignorefalse
-  \begingroup
-  \@endpefalse  % tmp!!! is it ok to drop this here?
-  \reserved@a}
-
-
-\cs_new:Npn \@kernel@math@registered@begin {
-%  \ShowTagging{struct-stack} 
-%\typeout{==>A1}\ShowTagging{struct-stack,mc-current}
-  \mode_if_vertical:TF
-       {
-%         \legacy_if:nTF { @endpe }
-%           { \legacy_if_set_false:n { @endpe } }
-%           { \__block_list_beginpar_vmode: }
-%
-%         \typeout{==>~ at:~ \g__tag_struct_tag_tl}
-%         
-         \exp_args:Noo\str_if_eq:nnF \g__tag_struct_tag_tl { \tpara }    % needs correction!
-             {
-%               \typeout{==>A2}
-               \__block_beginpar_vmode:
-             }              % needs correction!
-       }
-       {
-%         \typeout{==>A3}
-         \@kernel@close@P
-%         \tagmcend                      % needs correction!
-       }
-  \@kernel@math@begin
-  \tagpdfparaOff
-%  \typeout{==>MC1}\ShowTagging{mc-current}
-}
-
-\cs_new:Npn \@kernel@math@registered@end {
-%  \typeout{==>MC2}\ShowTagging{mc-current}
-  \para_raw_end:
-  \tagpdfparaOn
-  \@kernel@math@end
-%  \typeout{==>MC3}\ShowTagging{mc-current}
-  \@endpetrue
-}
-  
-\cs_new_protected:Npn \math_register_env:n #1
-  { \math_register_env:nn {#1} { } }
-\NewDocumentCommand \RegisterMathEnvironment { O{} m }
-  { \math_register_env:nn {#2} {#1} }
-%    \end{macrocode}
-% \end{macro}
-% \end{macro}
-% \end{macro}
-%
-% \begin{macro}{\@@_env_forward:w}
-%    \begin{macrocode}
-\cs_new_protected:Npn \@@_env_forward:w #1 \@@_env_end: #2 
-  { \@@_process:nn {#2} {#1} }
-%    \end{macrocode}
-% \end{macro}
-% 
-% \subsection{Document commands}
-%
-% \begin{macro}
-%   {\equation, \@@_equation_begin:, \equation*, \@@_equation_star_begin:}
-% \begin{macro}
-%   {\endequation, \@@_equation_end:, \endequation*, \@@_equation_star_end:}
-%   These environments are not set up by \pkg{amsmath} to collect their body,
-%   so we do that here. This has to be done \emph{after} we can be sure
-%   \pkg{amsmath} is loaded.
-%    \begin{macrocode}
-\tl_gput_right:Nn \@kernel@before@begindocument
-  {
-    \math_register_env:n { equation }
-    \math_register_env:n { equation* }
-% at the moment register_env can only do display math
-%    \math_register_env:n { math }
-    \RenewDocumentEnvironment{math} {b}{$#1$}{}
-% and this one doesn't work either    
-%    \math_register_env:n { displaymath }
-    \RenewDocumentEnvironment{displaymath} {b}{\[#1\]}{}    
-  }
-%    \end{macrocode}
-% \end{macro}
-% \end{macro}
-%
-% \begin{macro}{\(, \)}
-%  If math mode has not been collected, we need to  do that; otherwise, worry
-%  about whether we are in math mode or not. The closing command here can only
-%  occur inside a collected math block: otherwise it will be simply used as
-%  a delimiter.
-%    \begin{macrocode}
-\cs_gset_protected:Npn \( % \)
-  {
-    \bool_if:NTF \l_@@_collected_bool
-      {
-        \mode_if_math:TF
-          { \@badmath }
-          { $ }
-      }
-      {
-        \bool_set_true:N \l_@@_collected_bool
-        \@@_grab_inline:w
-      }
-  } % \(
-\cs_gset_protected:Npn \)
-  {
-    \mode_if_math:TF
-      { $ }
-      { \@badmath }
-  }
-%    \end{macrocode}
-% \end{macro}
-%
-% \begin{macro}{\[, \]}
-%   Again, we need to watch for when \pkg{amsmath} is loaded after this code.
-%   The flag usage here is to cover the case where \cs{[}/\cs{]} is hidden
-%   inside another environment. In this case the grabbing happens on
-%    the outer level and should not be repeated.
-%    \begin{macrocode}
-\tl_gput_right:Nn \@kernel@before@begindocument
-  {
-    \cs_gset_protected:Npn \[ % \]
-       {
-        \bool_if:NTF \l_@@_collected_bool
-          { \begin { equation* } }
-          { \@@_grab_eqn:w }
-      } % \[
-    \cs_gset_protected:Npn \]
-      {
-        \bool_if:NTF \l_@@_collected_bool
-          { \end{ equation* } }
-          { \@badmath }
-      }
-  }
-%    \end{macrocode}
-% \end{macro}
-%
-% \begin{macro}{\ensuremath}
-%   A bit of nesting fun to make sure we collect only if required.\fmi{why does ensuremath needs handling at all?}
-%    \begin{macrocode}
-%\cs_gset_protected:Npn \ensuremath #1
-%  {
-%    \mode_if_math:TF
-%      {#1}
-%      {
-%        \bool_if:NTF \l_@@_collected_bool
-%          { \@ensuredmath {#1} }
-%          {
-%            \bool_set_true:N \l_@@_collected_bool
-%            \@@_process:nn { math } {#1}
-%            \@ensuredmath {#1}
-%            \bool_set_false:N \l_@@_collected_bool
-%          }
-%      }
-%  }
-%    \end{macrocode}
-% \end{macro}
-%
-% \subsection{\cs{everymath} and \cs{everydisplay}}
-%
-% The business end for grabbing inline math and \enquote{raw} \TeX{}
-% display. Most display math mode is actually handled elsewhere, as we
-% have macro control.
-%    \begin{macrocode}
-
-\tl_new:N\tmpmathcontent
-
-  
-\def\@kernel@math@begin {
-%  \typeout{==>~math~begin}
-% needs different handling if we support nesting
-  \tl_gset:Nx\tmpmathcontent
-     {\exp_not:N\begin{\g__math_grabbed_env_tl}
-       \space
-       \exp_not:V\g__math_grabbed_math_tl
-       \space
-       \exp_not:N\end{\g__math_grabbed_env_tl} 
-    }
-  \tagstructbegin{tag=Formula,AFinline-o=\tmpmathcontent,alt=\tmpmathcontent}   %whatsits!
-% inner formula if multiple parts (not really implemented yet)
-  \grabaformulapartandstart
-% the above does:  
-%    \tagstructbegin{tag=Formula}\tagmcbegin{}
-%  or just
-% \tagmcbegin{}
-}
-\def\@kernel@math@end {
-%  \typeout{==>~math~end}
-%  \ShowTagging{struct-stack}
-  \tagmcend
-  \if@subformulas
-    \tagstructend
-  \else
-  \fi
-  \tagstructend
-%  \ShowTagging{struct-stack} 
-}
-  
-\exp_args:No \tex_everymath:D
-  {
-    \tex_the:D \tex_everymath:D
-    \bool_if:NF \l_@@_collected_bool
-      {
-        \bool_set_true:N \l_@@_collected_bool
-        \@@_grab_dollar:w
-      }
-  }
-\exp_args:No \tex_everydisplay:D
-  {
-    \tex_the:D \tex_everydisplay:D
-    \iftrue  % this may have to be a settable flag!
-%      {
-%        \typeout{==>~ in~ everydisplay}
-        \skip_set:Nn \belowdisplayskip      {-\belowdisplayskip}
-        \skip_set:Nn \belowdisplayshortskip {-\belowdisplayshortskip}
-        \int_set:Nn \postdisplaypenalty {10000}
-%
-        \group_insert_after:N \@@_tag_dollardollar_display_end:
-%      }
-    \fi
-    \bool_if:NF \l_@@_collected_bool
-      {
-        \bool_set_true:N \l_@@_collected_bool
-        \@@_grab_dollardollar:w
-      }
-  }
-%    \end{macrocode}
-%
-% \subsection{Modifying kernel environments}
-%
-%   We need to cover this even though it is of course not encouraged.
-%    \begin{macrocode}
-\math_register_env:n { eqnarray }
-\math_register_env:n { eqnarray* }
-%    \end{macrocode}
-%
-% Places where math mode is (ab)used.
-%    \begin{macrocode}
-\clist_map_inline:nn
-  { tabular }
-  {
-    \AddToHook{ env / #1 / begin }
-      { \bool_set_true:N \l_@@_collected_bool }
-  }
-%    \end{macrocode}
-%
-% \begin{macro}{\@@_m@th:, \m@th}
-%   Handle non-math use of math mode. At present nesting isn't supported as
-%   \cs{m@th} pops up in a few places that \emph{are} math mode!
-%    \begin{macrocode}
-\cs_new_eq:NN \@@_m@th: \m@th
-\cs_gset_protected:Npn \m@th
-  {
-    \bool_set_true:N \l_@@_collected_bool
-    \@@_m@th:
-  }
-%    \end{macrocode}
-% \end{macro}
-%
-% \subsection{Modifying \pkg{amsmath}}
-%
-% \begin{macro}{\@@_amsmath_align@:nn}
-% \begin{macro}
-%   {
-%     \@@_amsmath_gather@:n ,
-%     \@@_amsmath_multline@:n
-%   }
-% \begin{macro}{\align@}
-% \begin{macro}{\gather@, \multline@}
-%   Mark up all of the display environments as the content is captured anyway.
-%   We then use an internal macro in each environment type to insert the
-%   processing code. Each of these is slightly different, so we cannot use a
-%   simple loop here. The test for \cs{split@tag} is required as the
-%   \texttt{split} environment internally uses \texttt{gather} \emph{when not
-%   within an \pkg{amsmath}} environment, for example inside \texttt{equation}.
-%   Without the precaution, we'd get two copies of the grabbed math, the second
-%   of which would start with \cs{split@tag}.
-%    \begin{macrocode}
-
-
-
-\tl_gput_right:Nn \@kernel@before@begindocument {
-%
-\renewenvironment{gather*}{%
-  \start@gather\st@rredtrue
-}
-{%
-% this redirection doesn't work if we alter "gather"!
-  %  \endgather
-% so replace it with its real meaning
-  \math@cr \black@\totwidth@ \egroup
-  $$\ignorespacesafterend
-}
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-\def\common@align@ending {
-  \math@cr \black@\totwidth@
-  \egroup
-  \ifingather@
-    \restorealignstate@
-    \egroup
-    \nonumber
-    \ifnum0=`{\fi\iffalse}\fi
-  \else
-    $$%
-  \fi
-  \ignorespacesafterend
-}
-\renewenvironment{alignat}{%
-  \start@align\z@\st@rredfalse
-}{%
-  \common@align@ending
-}
-\renewenvironment{alignat*}{%
-  \start@align\z@\st@rredtrue
-}{%
-  \common@align@ending
-}
-\renewenvironment{xalignat}{%
-  \start@align\@ne\st@rredfalse
-}{%
-  \common@align@ending
-}
-\renewenvironment{xalignat*}{%
-  \start@align\@ne\st@rredtrue
-}{%
-  \common@align@ending
-}
-\renewenvironment{xxalignat}{%
-  \start@align\tw@\st@rredtrue
-}{%
-  \common@align@ending
-}
-\renewenvironment{align}{%
-  \start@align\@ne\st@rredfalse\m@ne
-}{%
-  \common@align@ending
-}
-\renewenvironment{align*}{%
-  \start@align\@ne\st@rredtrue\m@ne
-}{%
-  \common@align@ending
-}
-\renewenvironment{flalign}{%
-  \start@align\tw@\st@rredfalse\m@ne
-}{%
-  \common@align@ending
-}
-\renewenvironment{flalign*}{%
-  \start@align\tw@\st@rredtrue\m@ne
-}{%
-  \common@align@ending
-}
-%
-\renewenvironment{multline*}{\start@multline\st@rredtrue}
-{%
-  \iftagsleft@ \@xp\lendmultline@ \else \@xp\rendmultline@ \fi
-  \ignorespacesafterend
-}
-%    \end{macrocode}
-%    Also for "false?"
-%    \begin{macrocode}
-\def\measuring@true{\let\ifmeasuring@\iftrue\tag_stop:}
-%    \end{macrocode}
-%
-%    \begin{macrocode}
-%    
-  \math_register_halign_env:nn {align}{}
-  \math_register_halign_env:nn {align*}{}
-  \math_register_halign_env:nn {flalign}{}
-  \math_register_halign_env:nn {flalign*}{}
-  \math_register_halign_env:nn {gather}{}
-  \math_register_halign_env:nn {gather*}{}
-  \math_register_halign_env:nn {multline}{}
-  \math_register_halign_env:nn {multline*}{}
-  \math_register_halign_env:nn {xalignat}{}
-  \math_register_halign_env:nn {xalignat*}{}
-  \math_register_halign_env:nn {xxalignat}{}
-  %
-  \@namedef{maketag @ @ @} #1{%
-%    \typeout{--->maketag @ @ @}
-    \ifmeasuring@
-      \hbox{\m@th\normalfont#1}%
-    \else
-      \tagmcend \tagstructbegin{tag=Lbl}%
-      \tagmcbegin{tag=Lbl}%
-      \hbox{\m@th\normalfont#1}%
-      \tagmcend \tagstructend \tagmcbegin{}%
-    \fi
-  }
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-    \def\intertext@{%
-      \def\intertext##1{%
-        \ifvmode\else\\\@empty\fi
-        \noalign{%
-% we have to flip the sign on the skip because we flipped it on the outside
-          \penalty\postdisplaypenalty\vskip-\belowdisplayskip
-          \vbox{
-%    \end{macrocode}
-% Stop tagging when measuring:
-%    \begin{macrocode}
-           \ifmeasuring@\tag_stop:\fi
-           \normalbaselines
-            \ifdim\linewidth=\columnwidth
-            \else \parshape\@ne \@totalleftmargin \linewidth
-            \fi
-%    \end{macrocode}
-% End the previous mc:\fmi{if we use2 levels of formulas this would
-%    need changing}
-%    \begin{macrocode}
-            \tag_mc_end_push:
-%    \end{macrocode}
-% We are already in a par so we change now to Span:\fmi{not true any longer}
-%    \begin{macrocode}
-            \tagpdfsetup{paratag=P}%
-            \tagpdfparaOn
-            \noindent\ignorespaces\ShowTagging{struct-stack}##1\par
-%    \end{macrocode}
-% Restart the MC
-%    \begin{macrocode}
-            \tag_mc_begin_pop:n{}}%
-          \penalty\predisplaypenalty\vskip\abovedisplayskip%
-        }%
-      }
-    }
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-\@namedef{math@cr @ @ @ gather}{%
-    \ifst@rred\nonumber\fi
-   &\relax
-    \make@display@tag
-%
-    \maybestartnewformulatag
-%
-    \ifst@rred\else\global\@eqnswtrue\fi
-    \global\advance\row@\@ne
-    \cr
-}
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-\@namedef{math@cr @ @ @ align}{%
-  \ifst@rred\nonumber\fi
-  \if@eqnsw \global\tag@true \fi
-  \global\advance\row@\@ne
-  \add@amps\maxfields@
-  \omit
-  \kern-\alignsep@
-  \iftag@
-    \setboxz@h{\@lign\strut@{\make@display@tag}}%
-    \place@tag
-  \fi
-%
-    \maybestartnewformulatag
-%
-  \ifst@rred\else\global\@eqnswtrue\fi
-  \global\lineht@\z@
-  \cr
-}
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-\def\restore@math@cr{\@namedef{math@cr @ @ @}{
-%
-    \maybestartnewformulatag
-%
-    \cr}}
-\restore@math@cr
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-}
-%    \end{macrocode}
-% \end{macro}
-% \end{macro}
-% \end{macro}
-% \end{macro}
-%
-%
-%
-
-%  \begin{macro}{}
-%    
-%    \begin{macrocode}
-\cs_new:Npn \@@_split_at_nl_first:w #1 \\ #2 \\ #3 \s_stop
-  {
-    \quark_if_nil:nTF {#2}
-      { {#1} {  } }
-      {
-        \@@_split_chk_if_begin:ww #1 \begin \q_nil \s_mark
-          #2 \\ #3 \s_stop
-      }
-  }
-\cs_new:Npn \@@_split_chk_if_begin:ww #1 \begin #2 #3 \s_mark
-    #4 \\ \q_nil \\ \s_stop
-  {
-    \quark_if_nil:nTF {#2}
-      { {#1} {#4} }
-      {
-        \exp_after:wN \@@_split_collect_one_end:w
-          \@@_split_cleanup_begin_q_nil:w #1 \begin{#2} #3 \\ #4 \s_stop
-            { } { 1 }
-      }
-  }
-\cs_new:Npn \@@_split_cleanup_begin_q_nil:w #1 \begin \q_nil {#1}
-\cs_new:Npn \@@_split_collect_one_end:w #1 \end #2 #3 \s_stop #4 #5
-  {
-    \exp_args:Nf \@@_split_check_count_begins:nnnn
-      { \@@_split_count_begins:n { #4 #1 } } {#5}
-      { #4 #1 \end{#2} } {#3}
-  }
-\cs_new:Npn \@@_split_count_begins:n #1
-  { \int_eval:n { 0 \@@_split_count_begins:w #1 \begin \q_nil } }
-\cs_new:Npn \@@_split_count_begins:w #1 \begin #2
-  { \quark_if_nil:nF {#2} { +1 \@@_split_count_begins:w } }
-\cs_new:Npn \@@_split_check_count_begins:nnnn #1 #2 #3 #4
-  {
-    \int_compare:nNnTF {#1} = {#2}
-      {
-        \exp_last_unbraced:Nf \@@_split_final_cleanup:nn
-          { \split:n { \@@_split_guard:n {#3} #4 } }
-      }
-      {
-        \exp_args:No \use_ii_i:nn
-          { \exp_after:wN { \int_value:w \int_eval:n { #2 + 1 } } }
-          { \@@_split_collect_one_end:w #4 \s_stop {#3} }
-      }
-  }
-\cs_new:Npn \@@_split_final_cleanup:nn #1 #2
-  {
-      \exp:w \@@_split_final_cleanup:w #1
-        \@@_split_guard:n \q_nil \s_mark { }
-      {#2}
-  }
-\cs_new:Npn \@@_split_final_cleanup:w #1 \@@_split_guard:n #2 #3 \s_mark #4
-  {
-    \quark_if_nil:nTF {#2}
-      { \exp_end: { #4 #1 } }
-      { \@@_split_final_cleanup:w #3 \s_mark { #4 #1 #2 } }
-  }
-\NewDocumentCommand \splitnl { mm +m }
-  {
-    \tl_set:Nf \l_tmpa_tl { \split:n {#3} }
-    \show \l_tmpa_tl
-    \exp_after:wN \__splitnl_aux:nnNN \l_tmpa_tl #1 #2
-  }
-
-
-\cs_new:Npn \split:n #1 {
-    \@@_split_at_nl_first:w #1 \\ \q_nil \\ \s_stop }
-
-\cs_new:Npn \@@_split_at_nl:NN #1#2 {
-  \tl_set:Nf \l_tmpa_tl {
-      \exp_after:wN \@@_split_at_nl_first:w #1 \\ \q_nil \\ \s_stop }
-  \exp_after:wN \@@_split_at_nl_aux:nnNN \l_tmpa_tl #1 #2
-}
-
-\cs_new_protected:Npn \@@_split_at_nl_aux:nnNN #1 #2 #3 #4
-  {
-    \tl_gset:Nn #4 {#1}
-    \tl_gset:Nn #3 {#2}
-}
-
-%    \end{macrocode}
-%  \end{macro}
-%
-%
-%  \begin{macro}{\maybestartnewformulatag}
-%    
-%    \begin{macrocode}
-
-\newif\if@subformulas
-\tl_new:N \result  
-  
-\cs_new_protected:Npn\grabaformulapartandstart {
-  \@@_split_at_nl:NN  \g__math_grabbed_math_tl \result
-  \typeout{====>first-result=\meaning\result}
-  \typeout{====>first-tmpmathcontent=\meaning\g__math_grabbed_math_tl}
-  \tl_if_empty:NTF \g__math_grabbed_math_tl
-     {
-       \typeout{====>formula~ has~ no~ subparts}
-       \global\@subformulasfalse
-     }
-     {
-       \typeout{====>formula~ has~ subparts}
-       \global\@subformulastrue
-       \edef\resulttitle{\g__math_grabbed_env_tl\space (part)}
-       \tagstructbegin{tag=Formula,alt=\result,
-         title-o=\resulttitle}
-    }
-    \tagmcbegin{}
-}
-
-\cs_new_protected:Npn\grabaformulapartandmayberestart {
-  \@@_split_at_nl:NN  \g__math_grabbed_math_tl \result
-  \typeout{====>result=\meaning\result}
-  \typeout{====>tmpmathcontent=\meaning\g__math_grabbed_math_tl}
-%  \tl_if_empty:NTF \g__math_grabbed_math_tl
-%     {
-%       \typeout{====>tmpmathcontent=empty}
-%     }
-%     {
-%       \typeout{====>tmpmathcontent=not-empty}
-       \edef\resulttitle{\g__math_grabbed_env_tl\space (part)}
-       \tagstructbegin{tag=Formula,alt=\result,
-         title-o=\resulttitle}
-%    }
-    \tagmcbegin{}
-}
-%    \end{macrocode}
-%  \end{macro}
-%
-%
-%
-%
-%    \begin{macrocode}
-\def\maybestartnewformulatag {
-\if@subformulas
- \ifmeasuring@\else
-%
-  \tl_if_empty:NF \g__math_grabbed_math_tl
-     {
-       \tagmcend 
-       \tagstructend
-       \grabaformulapartandmayberestart
-     }
- \fi
-\fi
-}
-%    \end{macrocode}
-%
-%    The breqn packages changes catcodes and that isn't yet covered
-%    by our mechanism.
-%    \begin{macrocode}
-%\AddToHook{package/breqn/after}{
-%  \typeout{===>~ in~ hook}
-%  \math_register_halign_env:nn {dmath}{}
-%  \math_register_halign_env:nn {dgroup*}{}
-%}  
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-\ExplSyntaxOff
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-%<@@=>
-%    \end{macrocode}
-%    
-%    \begin{macrocode}
-%
-%    \end{macrocode}
-%
-%    \begin{macrocode}
-%</kernel>
-%    \end{macrocode}
-%
-% \Finale
-%
diff --git a/required/latex-lab/latex-lab-mathtagging.dtx b/required/latex-lab/latex-lab-mathtagging.dtx
index 84c380996..19ca1a4ef 100644
--- a/required/latex-lab/latex-lab-mathtagging.dtx
+++ b/required/latex-lab/latex-lab-mathtagging.dtx
@@ -21,7 +21,7 @@
 %<*driver>
 \documentclass{l3doc}
 \EnableCrossrefs
-\CodelineIndex
+\CodelineIndex 
 
 \usepackage{todonotes}
 
@@ -62,6 +62,8 @@
 % \tableofcontents
 %
 % \section{Introduction}
+% \car*{Todo: update all the documentation! Both here and 
+%   (what little there is!) in the implementation section.}
 %
 % This file implements capture of all math mode material at the outer
 % level, i.e., a formula is captured in its entirety with inner text
@@ -116,8 +118,62 @@
 %       material.
 %   \end{itemize}
 % \end{function}
+% 
+% \section{Known current bugs, etc.}
+%     \car*{New Section, now with subsections.\\
+%      As indicated, these lists are probably incomplete.\\
+%      Some of these have been addressed in a more recent branch.} 
+%
+% \subsection{Capture/grabbing problems}
+% 
+% \begin{enumerate}
+%   \item Incorrect grabbing of |$|-math when there is also 
+%      explicit |$|-math within a \textit{text environment} 
+%      that is itself within the math that should all be grabbed.
+%   \item Similar incorrect grabbing with |$$| also.
+%   \item The grabbing, for all the display environments (and |\) \]|), needs
+%       to deal with nesting: \pkg{amsmath} contains code for this. 
+%   \item 
+% \end{enumerate} 
+%
+% \subsection{Other problems}
+% 
+% \begin{enumerate} 
+%   \item 
+%      The presence of \cs{m@th} in association with \cs{ensuremath} 
+%      does not necessarily indicate fakemath.  This is because  
+%      wanting mathsurround to be zero is very reasonable and common, 
+%      \emph{even when the math is genuine} (and hence needs to be collected).
+%   \item User-defined environments can create problems; but this area, of 
+%      new, copied and changed environments, has not yet been developed. 
+% 
+%  \car*{Joseph wrote, inter alia:\\
+%      My thinking [regarding] \cs{RegisterMathEnvironment}\\
+%    - (New) Math environments should not be created-then-patched, but only
+%    generated by a [(future)] dedicated command (\cs{DeclareMathEnviornment}, 
+%    presumably)\\
+%    - Math environments created with \pkg{ltcmd} [commands] should not be copied, . . .\\
+%    - Package authors should be able to manually set up math environments with a public boolean.}
+%
+%   \item 
+% \end{enumerate} 
+%
+%
+% \subsection{Other ToDos}
+%
+% \begin{enumerate}
+%  \item Add (some of) the math display commands that were \enquote{lifted from 
+%    plain}, e.g., \cs{displaylines} \cs{eqalign}(??).
+%  \item 
+% \end{enumerate}
 %
-% \MaybeStop{\setlength\IndexMin{200pt}  \PrintIndex  }
+%
+% \car*{\cs{MaybeStop} (temporarily) not executed, as it is unknown on Chris' system.}
+% \iffalse
+%  \MaybeStop{\setlength\IndexMin{200pt}  \PrintIndex  }
+% \else
+%  \StopEventually{\setlength\IndexMin{200pt}  \PrintIndex  }
+% \fi
 %
 % \section{The Implementation}
 %
@@ -130,6 +186,8 @@
 %    \end{macrocode}
 %
 % \subsection{File declaration}
+%
+%    \car{Change description here?}
 %    \begin{macrocode}
 \ProvidesFile{latex-lab-mathtagging.ltx}
         [2023-02-06 v0.5a Grab all the math(s) and tag it (experiments)]
@@ -153,15 +211,24 @@
   { \RequirePackage { amsmath } }
 %    \end{macrocode} 
 %
+%
 % \subsection{Data structures}
 %
-% \begin{variable}{\l_@@_collected_bool}
+%
+% \car{if $=>$ whether, below}
+%
+% \begin{variable}{\l_@@_collected_bool} 
 %   Tracks if math mode material has been collected, which happens inside
 %   \pkg{amsmath} environments as well as those handled directly here.
+%
+%
 %    \begin{macrocode}
 \bool_new:N \l_@@_collected_bool
 %    \end{macrocode}
 % \end{variable}
+% 
+%  \car{Change first tl name below: `env' $=>$ `info'?\\
+%        Or do we need an extra storage tl?}
 %
 % \begin{variable}{\g_@@_grabbed_env_tl, \g_@@_grabbed_math_tl}
 %    \begin{macrocode}
@@ -209,6 +276,17 @@
 % \begin{macro}{\@@_grab_dollar:w}
 %   Grab up to a single |$|, for inline math mode, suppressing
 %   any processing if the first token is \tn{m@th}.
+%
+%    \fmi{what's that test doing?} 
+%
+%    \car{It is some kind of fix, to avoid the remote 
+%      possibility that the math is empty, making the code 
+%      produce an unwanted \texttt{\$\$}.} 
+% 
+%\car{cf.~the code for this in \cs{@ensuredmath}} 
+
+%\car{It is harmless but unnecessary in the dollardollar grabbing below.}
+%
 %    \begin{macrocode}
 \cs_new_protected:Npn \@@_grab_dollar:w % $
   #1 $
@@ -288,6 +366,7 @@
 %    \end{macrocode}
 % \end{macro}
 %
+%
 % \begin{macro}{\@@_grab_inline:w}
 %   Collect inline math content and deal with the need to move to math mode.
 %    \begin{macrocode}
@@ -349,8 +428,8 @@
 % \begin{macro}{\math_register_env:n}
 % \begin{macro}{\RegisterMathEnvironment}
 %   Set up to capture environment content and make available.
+% 
 %    \begin{macrocode}
-
 \cs_new_protected:Npn \math_register_env:nn #1#2
   {
     \tl_set:Nn \l_@@_env_name_tl {#1}
@@ -550,7 +629,12 @@
 %    \end{macrocode}
 % \end{macro}
 % 
-% \subsection{Document commands}
+% \subsection{Document commands} 
+%
+% \car*{Add one more here: \texttt{displaymath}, which
+%        is equivalent to \cs{[} , \cs{]}\\
+%        and hence to the basic \texttt{equation*}.\\
+%       Added in more recent branch.}
 %
 % \begin{macro}
 %   {\equation, \@@_equation_begin:, \equation*, \@@_equation_star_begin:}
@@ -559,6 +643,11 @@
 %   These environments are not set up by \pkg{amsmath} to collect their body,
 %   so we do that here. This has to be done \emph{after} we can be sure
 %   \pkg{amsmath} is loaded.
+%
+% \car*{Note that with \pkg{amsmath} loaded, \texttt{equation*} and \texttt{equation}\\
+%        are the two basics: they are used to define the other single-row\\
+%        display environments, etc.}
+%
 %    \begin{macrocode}
 \tl_gput_right:Nn \@kernel@before@begindocument
   {
@@ -626,9 +715,16 @@
   }
 %    \end{macrocode}
 % \end{macro}
+% 
 %
 % \begin{macro}{\ensuremath}
-%   A bit of nesting fun to make sure we collect only if required.\fmi{why does ensuremath needs handling at all?}
+%   A bit of nesting fun to make sure we collect only if required.
+%   \fmi{why does ensuremath need handling at all?}
+% 
+%   \car{Indeed!  Currently, this is setup to process the math that 
+%     it has anyways already captured as its argument; thus it is more 
+%     efficient than leaving the capture to be repeated by the \cs{everymath}}
+% 
 %    \begin{macrocode}
 %\cs_gset_protected:Npn \ensuremath #1
 %  {
@@ -1153,3 +1249,5 @@
 %
 % \Finale
 %
+% 
+