By far the most customizable and efficient tab tree extension for sidebar style tabs. Combine this with some userChrome tweaks, and you have the perfect setup.

keeps resetting my whole tab collection. I like it a lot , but it keeps doing this every time I open Firefox after bootup
Update: 26.5.2022
Still messing with the structure of the groups. I am so sad, since this is the best way to use tree style tabs. Please fix it

This is seriously the best extension of all time! This is more than just a tab manager or verticle tree tabs extension. It does offer that as a basic feature but offers SO much more. The new beta version you can find on the extension's Github makes the extension even better. Highly recommended for any power user!

It seemed very promising at first but this extension just did not work for me. Every time I would close Firefox led to losing my tabs and the organisation. The sync function didn't seem to work.

I'm one of those people who like to have 100+ tabs open. This add-on is by far the the best option for managing those tabs on Firefox.
Thank you or the amazing work!

"Dieses Add-On ist ausgezeichnet. Für meinen Anwendungsfall sind Webbrowser ohne so etwas grundsätzlich unbrauchbar. Ich war jahrelang auf der Suche nach so etwas, das tatsächlich gut funktioniert, mit vielen Enttäuschungen auf dem Weg. Es gibt mehrere Add-Ons zum Organisieren von vertikalen Registerkarten, aber dies war bei weitem das stabilste für mich. Ich hatte einige Fälle, in denen Tab-Gruppen verloren gingen, aber das Einstellungsmenü enthält einen Vorschlag zur Behebung dieses Problems (unter „Wo Tabs gespeichert werden“), was bei mir funktioniert zu haben scheint. Es sieht auch gut aus, funktioniert gut und hat viele anpassbare Optionen. Ein Vorschlag ist, die Option zu haben, die Registerkartengruppennamen neben oder als Alternative zu den Symbolen anzuzeigen. Vielleicht übersehe ich diese Option irgendwo.,,

This add-on is excellent. For my use case, web browsers are basically unusable without something like this. I've been on a a years long search for something like this that actually works well, with many disappointments along the way. There are several vertical tab organizing add-ons out there, but this has by far been the most stable one for me. I did have some instances of tab groups being lost, but the settings menu provides a suggestion for fixing this (under "Where to store tabs") which seems to have worked for me. It also looks good, functions well, and has lots of customizable options. On suggestion is to have the option to display the tab group names along side, or as an alternative to, the icons. Maybe I'm missing this option somewhere.

Been looking for an extension to keep my pinned tabs open after I close Firefox. This seems to be doing the trick :).

Has a ton more options that I have yet to dive into :D.