Literally the reason I use Firefox over Chromium browsers.

Чудове розширення. Забрав зверху панель вкладок)

Bestes Addon! Sehr praktisch! Ich empfehle auch die anderen Addons die Tree Style Tab erweitern anzuschauen.

私にとって最早不可欠な拡張です。

I've been using Tree Style Tab for years. Occasionally it reloads (as in seems to close itself and reopen), but otherwise has performed flawlessly. It's a staple add-on for me, and is a big reason I use FireFox.