I have to use it longer but this may be even better than Tree-Style Tabs (which is very good, to be clear)

Replaces with benefits both Tree Style View and Simple Tab Groups. The first one still is great. The latter is very buggy. But Sidebery replaces both, with an smooth experience

This extension is the main reason why I give up on Chrome. Especial when Google closed a sync with Chromium.

The main reason I moved to Firefox. Like TST but consolidated with even more features. Has a few kinks to work out... looking forward to v5.

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.

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!

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!

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.