Tree Style Tab is available on Firefox Quantum and will be with us for a long, long time. Piro, the author, wrote an excellent article about his experience porting TST to a WebExtension: http://piro.sakura.ne.jp/latest/blosxom/mozilla/extension/tr...

Nice extension, but no search for tab option. For now I use Firefox built-in option to search for tab: open new one and start typing the title of tab, I want to find. The drawback: that search is VERY dumb and you have to exactly type the proper name, no fuzzy logic or smth at all.

I got the new Tree Style tabs installed, but I'm still seeing the standard tabs at the top, is there a way to hide those?

I asked this exact question on Stack Overflow earlier today and found that someone else had already also asked it and got an answer.

https://superuser.com/questions/1261660/firefox-quantum-ver-...

(basically, hacking some CSS rules by creating a file in your AppData directory, so that the top bar is hidden)

Incidentally, I also discovered that Tree Style Tab's settings page under Firefox has a nice little box where you can configure the CSS it uses, which was nice because I prefer it with a smaller font and less padding.

What uglycoyote commented is the stopgap solution for now, but an API for doing that is in the works, so in a few versions from now, you shouldn't need that more-or-less hack anymore.