Great, but it needs a search bar, to look for the tab you can't find (because there are too many, or because it is in a collapsed group).

5/5 until recent update, I don't know how to remove the new "Tree Style Tab" header in the sidebar above all my tabs but below bookmarks. 2/5 until this is fixed

Very useful tool white managing abundant tabs!

Very good idea unfortunately looks ugly

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Cool

Extremely useful for organisation

However, it does often glitch in one particular way. I keep it on the right side of my desktop, but sometimes the formatting gets messed up where the crosses all appear on the left and the down arrows on the right, with no indentations below each tree, undermining its utility

閉じたタブを開き直す で最後に閉じたタブだけじゃなくて直近10件くらいから選択できたら嬉しい

It's a good addon. I can't use firefox without it. However the recent update seems to be greying out some (but not all?) discarded tab favicons when I already have something to display that they've been discarded.
I tend to recognise tabs in part by favicon colour; is there a way to disable this behaviour? Nothing in the options for Tree Style Tab. Recent updates mentions some 'secret options' and I've no idea how to even access those.

Besides that, Tree Style Tabs sometimes loses the highlight of the active tab, and the only way you can identify it is mousing over all tabs and checking which one doesn't highlight.