After using it, now I need this in every browser I use.
Side note: If someone wants to hide upper tabs, they can do so using custom css or install addons.mozilla.org/en-US/firefox/addon/toggle-native-tab-bar/

Overall looks great and works well, but when it's active I can't right-click on tabs to bookmark them. When I try to do this, nothing happens. I tried creating a new profile and the problem is still there. Only when I disable the extension am I able to add bookmarks in this way.

Très bien, très pratique, mais l'installation provoque un comportement inattendu dans les autres fenêtres de Firefox dont le panneau latéral n'est pourtant pas réglé sur Tree Style Tab (sur marques pages, par exemple) : les nouveaux onglets s'ouvrent alors dans n'importe quelle position, et non pas à côté de l'onglet qui en a directement commandé l'ouverture. Une solution ???
Si je désactive temporairement Tree Style Tab, le comportement d'ouverture des nouveaux onglets redevient normal !

sangat membantu BINTANG 10!!

It only adds a second tab bar down the side, but you still can't get rid of the one across the top, so more space is wasted without increasing the depth of the useful space. You to think either Chrome or Firefox programmers would realize there's no need for a tab section at all if you only have one URL open.

Nice, although a bit slow every time when it's opened.
A live search/filter on top would be great (getting focus when side bar is opened)

One of my top 3 favorite add-ons for all of Firefox!

I HAVE ONE FEATURE REQUEST PLEASE!

Please add re-naming tabs and allow me to turn the feature on from the Context Menu or Tree Behavior section.

Pleaseeee!