So much more responsive and performant than Tree Style Tab (aka TST) if you have way too many tabs open. This is the one you want.

Perfect

I really don't know how I lived without it before.

Looking for something much, much simpler to use. All I want to do is to quickly group tabs.

Make setting for default panel (bookmars or tabs or ...). I need bookmarks, but it allways open tabs first.

Excellent extension. So much more than just vertical tabs. Panels can be configured to match containers.

Would highly recommend.

it's a great add-on but I'm having a problem with it.
It doesn't work properly with browser.tabs.closeWindowWithLastTab firefox preference.
I have to deactivate it first.

This is the best vertical tab extension. I have disabled horizontal tabs using css so now it looks like it was built in.

If you shift-click select in a search filtered view it selects tabs that aren't shown due to the filter. How did anyone think that was a good idea? User hostile design choice

I was fighting with tabs for so many years. Constantly having a multitude of open tabs, fearing accidentally closing the window.

I was not very productive, having to scroll and look for tabs all the time.

After making the leap to Tree Style Tab, I got comfortable with vertical tabs, and just recently I made the swift to this, more powerful, version.

There are SO many things to configure. Lots of small tweaks. I loved making the sidebar my very own, even implementing a bit of userChrome.css.

This add-on is extremely powerful, as it's so versatile.

I will never look back from this day!

It would be nice to be able to see "synced tabs" in tab panel.