Uploads of some extra pandoc material which might be of interest to others.
numbered-sections.docx, a docx-template for numbered sections. Created by 1) making a docx-file through pandoc and 2) numbering sections manually. Can now be used as a reference docx as follows:
pandoc INPUT --reference-doc=numbered-sections.docx -o OUTPUT.docx
Headings for levels 1-3 are numbered. E.g. section, subsection, and subsubsection. Headings on level 4 and lower are not numbered.