Essential

Supporting for FF57+ is awesome!

BTW, does WebExtension has no API to hide native tab bar?

I tried other browsers, but without vertical/tree style tabs they were just unuseable for me. I can't understand why this isn't the default tab UI for all browsers implemented without any extension.

Works great.

The one thing that bothered me enough (apart from hiding the top tabbar with the userChrome changes mentioned in another review) is the fact that the tabs are padded too much for my taste.

Luckily there's a "Extra style rules for sidebar" textarea in the options page, where you can put extra CSS rules for the sidebar. I've added the following in that textarea:
/* slimmer tabs in sidebar */
.tab {
padding: 1px;
}

嬉しい！

Until mozilla gets around to creating the API to hide the tab bar, do this:

Go into about:config and set browser.tabs.drawInTitlebar to false

Go into about:profiles, click Open Folder on root directory, create or open the "chrome" folder and create or edit a "userChrome.css" file in that folder (capitalization counts, even on Windows). Enter the below in the userChrome.css file, save it, close and restart Firefox:

/* Hide tab bar */
#TabsToolbar { visibility: collapse; }
#sidebar-header { display: none; }

absolutely elated that TST will be 57+ this is the only add-on I cannot live without and why I use Firefox exclusively. Thank YOU! Piro

以前のバージョンと比べると再起動したときに勝手にツリーが崩れていたりするバグが無くなっていたり、見易さが向上していたりでかなり使いやすくなった様に思います。
しかし、上部にあるFirefoxデフォルトの横型タブは以前のTreeStyleTabの様に消す（見えなくさせる）事は出来ないのでしょうか？
オプションを見てもそういう風な設定は無さそうです。Firefox側で制限されていたりするというのならば仕方ありませんが...

もう一つ、オプションでテーマを設定してもTreeStyleTab最上部のサイドバーを閉じるボタンがある部分の色が変わらないのは仕様でしょうか？Firefox側のテーマもTreeStyleTabのテーマと合わせて暗色系にしたのですが、そこだけ白くなっており、他の部分と比べ少し浮いているのが気になります。

edit: なるほど...わざわざbugzillaへのリンクも貼っていただき感謝します、そういうことなら仕方ないですね。Firefox側の対応に期待して首を長くして待つことにします。

it works on 57!

Great!

Been using TST for many years and was afraid I'd lose my favorite extension after Quantum v57 upgrade. Thank you Piro!

You sir, are a hero.

And those who want FF to look like it did with the previous version of Tree Style Tabs, see the hints here: https://news.ycombinator.com/item?id=15342728

I am really glad this extension now supports FF 57+. Now I can return using Firefox.

Can you add compatibility with 55?

Working with a lot of tabs is a huge pain - but now I am able to organize them and not loose track. Please keep the updates coming.