I would give this extension 1 star, but I can't. Because this is the only one extension, which works for saving and restoring sessions for Firefox. There is no alternative.
I can't give 5 stars however, because extension is very buggy and looks like not even tested by developer properly.

Obvious issues are:
1) If you move tabs between windows - then session tracking gets screwed up Tab Session Manager cannot save this session anymore. Nothing helps. I tried disable/enable back extension. I tried remove extension from Firefox and re-install it back. Nothing helps. Moving tabs between windows is Firefox core functionality. Also its possible to move tabs between private windows. This makes it impossible to organize tabs across multiple windows when using Tab Session Manager.
2) Tab Session Manager export-import extension settings - doesn't work properly. After you import settings you notice that many options are not respected by export and do not restore back. A lot to list them all, but for sure I remember: theme, auto-save intervals, backup and other options.
3) Keyboard shortcuts for saving sessions - do not work at all. No matter which key combination, I tried everything. Only one shortcut works - open extension menu drop down.
4) Bug in intervals. If you set interval to 60 minutes - nothing gets saved every hour. I had to set to 50 minutes because of this.
5) If tracking is screwed up because any unknown reason - then it's impossible to reload extension and re-capture current session and it will always fail to save current session.

But what really works great is regular popup that asks about donations.
I would happily donate, but currently I am not aware if developer cares at all about above mentioned issues, whether those will get fixed.

Help, all my sessions saved in the last 3 years have disappeared. I hope developer notices and helps me

It seems to do most of what I expected. One part I had hoped is that it would remember window placement (where are they on screen ... and which virtual desktop are they on). Unfortunately, it doesn't do either. For me, this just seems to be another way to do what "Restore Session" already does.

Does not work. File has the data inside it, yet this add on does nothing with it.

Powerful. Vastly superior to bookmarkiof ng, best way to conserving extensive web research.

Facebook und X starten oft nicht im aktuellen Fenster, sondern machen eigene Fenster auf. Wenn ich vergesse, diese Fenster zu schließen, bevor ich Firefox beende, kann es passieren, dass beim nächsten Firefox-Start alle meine Tabs weg sind und stattdessen Facebook oder X startet. In solchen Situationen hat mir Tab Session Manager schon oft die Tabs wiederhergestellt.

Very interesting extension, but there are shortcomings, especially in terms of optimizations after 1000+ saved sessions it starts to lag, freeze, etc., developers, do something about this, optimize the list of sessions so that when you open the menu, not all sessions are loaded at once, but in parts, or make a page mode instead of scrolling, otherwise it’s a complete disaster with the list of sessions!!!, and by the way, for some reason, the extension works better and faster on Chrome than in Mozilla, but there too, if you save a lot of sessions, it starts to freeze, but in Chrome there is also session-buddy, also good, I recommend it, it’s a pity there is no Tab Session Master analogue for Mozilla.

It would be a very great extension but unfortunately it cannot work together the Tree Style Tab. Yes I know it says it can but it's not true. It can restore the tabs with Tree Style Tab in 1 time of 10 attempts, in other cases I lose the Tree Style Tab settings, what is very annoying and I don't says polite words during that time when I have restore the trees manually. What is not a funny process with more hundreds tabs.

one of th most important addons for FF!
thank you.
BEST: sync with cloud.

One of my most used extensions. I wish it was available for Firefox on Android.

Ele funcionava bem há alguns anos, mas não salva mais as sessões automaticamente, seja por tempo, seja ao sair do Firefox, somente salva quando salvamos manualmente - e, mesmo assim, pode manter apenas a última.