/After upgrading to Thunderbird 115 (Fedora 38) and Quickfolders 6.3 then using the Shift-M shortcut to move mails and folders only works for mails and not folders.
If I have the Error Console open while pressing Shift-M and having selected a folder in the folder pane, then the following error appears:
Uncaught ReferenceError: gFolderTreeView is not defined quickfolders-interface.js:1870:31
windowKeyPress chrome://quickfolders/content/quickfolders-interface.js:1870
keyListen chrome://quickfolders/content/quickfolders.js:719
[Learn More]
windowKeyPress chrome://quickfolders/content/quickfolders-interface.js:1870
keyListen chrome://quickfolders/content/quickfolders.js:719