Works really well, although need to understand settings and that Firefox now has a similar feature biult-into itself, which saves users from many annoyances or even troubles.

Good to have both if closing browser with many windows happens often to you.

After may similar I tried, this one is most stable and for me do the job perfectly Thanks Sienori!

Addon is very useful but restore of sessions don't working

Useful addon.
Please create a sort function all tabs by url like
jkljlk.host1.url
jkljljgg.host1.url
jhg.host2.url
jhgjkh.host2.url

タブの保存に、素早く元のタブを開けるこのアドオンが大変便利です。
ただ、このアドオンのバグか、ほかのアドオンの影響かはわかりませんが、現在のウィンドウで開くと、一番左端にあるタブが、一番右端で開くようになってしまいました。
解決方法はありますか？

It does what it should and that very good for me since 2 months.
But when restarting FF and opening last session via Tab Session Manager the tab order ist lost. I did tests now by saving and reopen of a (one) window:
Reopening works fine when active tab is the most right one.
Atherwise only the tabs left to the active one are correct after reopening. The tabs to the right of the active one are reopened in wrong order.
What I found saving is not the problem it's the reopening !
Whould be nice to hear if you found that as i do and more nice if you would correct this issue.
kr johann

awesome addon and the developer is very helpful

Of the many tab managers I tested, Tab Session Manager is the one I love and use most. I has all the functionality I need implemented in a lean, efficent and no-frills way. Easy to understand, trivial to learn and has never failed me (using it about a year now).

It comes with built in manual sync to your own google drive account (no 3-rd party servers or sign-ups in between Firefox and your G-drive account).

It auto-backups all your Firefox windows & tabs automatically locally (time interval can be set in user settings) and is the best browser crash-insurance to date.

Tab Session Manager is a well designed, cross-browser and efficient FLOSS extension: Free (as in free beer), Libre (as in liberte, egalite, fraternite) and Open Source Software, with code access on github. It is well documented and in continuous feature development and bug maintenance (due to the ever evolving browser API changes).

My warm gratitude to the main developer @sienori on github.com

How about add features:
> Add to current tab to session group.
> Override session group with current window tabs.
> Always show searchbar.
> Order group by drag.
> Provide recycling bins.

saved my a*s off

Great add-on, just what I needed. Many thanks!