This plugin was one of the reasons why I moved back to use Firefox. This feature should be default in all the browsers.

@Alexandru Nedelcu -- Any way to restore the window control buttons (e.g., min, max, close)?

TST is a great addon, but the need to continually write your own CSS code to make it behave within reasonable expectations is frustrating. Moreso, the changing css code makes this work-around unreliable; see above. The latest change to FF has rendered the previous solutions obsolete: eliminating the duplicate horizontal tabs using the previous method also eliminates the window controls.

The horizontal tab bar can be hidden via userChrome.css, see: https://gist.github.com/alexandru/0f8b9a845342dd919d48dccc844a7135

This is the addon that keeps me locked to Firefox - I simply can't move to a browser without vertical tabs. Thank you, Piro.

best extension

This great addon is the main reason why I'm using Firefox.

導入してからタブを探し回る事が減りました。

サイドバーにタブを表示するアドオンは他にもいくつかありますが、複数の階層に分けて分かりやすく整理できるものはこれだけだと思います（派生型を除く）。

Vivaldiのようにサムネイルも表示できればなお良し。

希望能够出一个chrome版的tree style tab，感谢作者。
Hope there is one in the chrome, thank you, great author of great plugin