#25 Thanks for the tip. I just downloaded the add-on below.
Tab Session Manager - it puts an icon on the main toolbar. Save 1 or all tabs. Highlight a tab you want restore and click on a square icon or the trash can to delete.
https://addons.mozilla.org/en-US/firefox/addon/tab-session-manager/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search
You can a click group and restore the group.