The existing popup menu lists all the notebook tabs first then shows command items below. This means the command items are harder to access (user has to move mouse further). They can also get pushed off screen when there are many tabs open (see https://github.com/geany/geany/pull/2346#issuecomment-539842133). Instead, let's split up the menu for better UX.
New notebook action widget menu, left or right click ☰ button: 
Commands-only tab menu: 
The single close item has been grouped separately and put first because:
> This will be the most common choice for anyone who disables notebook tabs. This also groups the commands closing multiple documents separately from the other commands. Closing multiple documents is a more drastic action so should be grouped separately. You can view, comment on, or merge this pull request online at:
https://github.com/geany/geany/pull/2348
-- Commit Summary --
* Use gtk_widget_show_all in show_tab_bar_popup_menu * Remove unnecessary casts * Notebook tab menu: Move tab filenames to button menu at end of tabs * Move single close item to top of menu
-- File Changes --
M src/notebook.c (56)
-- Patch Links --
https://github.com/geany/geany/pull/2348.patch https://github.com/geany/geany/pull/2348.diff