bugs/firefox-bookmark-all-tabs-shortcut.md

https://support.mozilla.org/en-US/kb/tabs-organize-websites-single-window#w_tab-tips

To bookmark a set of tabs all at once use the keyboard shortcut Ctrl + Shift + D.

This one appears to be a documentation bug, since by all accounts the option is deliberately gone from the top-tier menus, having been relegated to the tabs contextual menu.