Rated 5 out of 5 stars

le Firefox user 9a6ac3 ar Samh. 15, 2017 · buan-nasc

Probably one of the best add-ons for FF and one of the reasons I do use FF. I did donate. I will donate again for a Quantum (FF 57+) version.

UPDATE: it seems Michael will not update this for Quantum (FF57+). I suggest switching to TabZen. Start FF (pre 57, like the ESS Version) with Session Manager and TabZen. Open your sessions you want to keep and save them with TabZen to a Folder. After you Update you can open the tabs in the folders with TabZen.