I had one window open with dozen of tabs and another with a single tab.
Now Microsoft decided the system had to be closed down and did this without any further warning.
When I start Firefox after this, the window with the single tab opens and although I can 'restore previous session', that only restores this window with the single tab, but I would want to restore the window with the dozens of tabs.
These tabs represent a lot of work and point to web pages where I am interested in and/or am working with.
Although from the history, I can retrace some of these pages (those that I have used recently), others remain gone and I have to dig deep in my memory to find out exactly where they were pointing to.
I have always checked the option in preferences under startup of 'open previous windows and tabs'. Recently Firefox deletes all my tabs when restarting the computer. I hate hate hate this!! And there is no 'restore tabs from previous session' option anywhere.