Like it.
Gives me the freedom to use those extra couple of cm's at the top of the screen, by utilising the side of the screen a bit.
Been using it now several years.

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.

SUPER

I expect that tabs are grouped automatically by root domain search on top in text box by words.

I really like what this add-on does. The problem is that it never stops doing it. I have tabs that need to be in a tree structure. That part is great. But I don't want new trees created every time I run a Google search or open a new tab from an existing page. Sadly, there seems to be no way to control that. So if I want to use this add-on at all, I have to manually flatten every newly created tree. It is a chore, and it seems unnecessary.

how about a version for vivaldi? it have sibebar panel too

Just found this, love it! :D

Pretty simple, works great, excellent for organisation and power users with MANY tabs :D

długo używam ten styl i dobrze się sprawuje

I cannot imagine using a browser without it. It's a pity that Firefox breaks compatibility and right now my main issue is that I cannot share tabs between devices.