show tabs from last time and clean history
I enable the following: when firefox starts: show tabs from last time when firefox closes: clean history
But firefox does not show tabs from last time and my tab groups also gone. I think these two setting are two distinct features and should not conflict each other. Otherwise, it becomes private browsing!
Alla svar (1)
Clear (Browsing) History clears everything, on exceptions, and that includes tabs that are still open when you close Firefox, so you do not have to close those yourself.
So if you want to reopen tabs from the previous session then you can't clear the history on exit, but you need to do that yourself manually before closing Firefox.