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.

Great sidebar extension with a ton of customization options, even more if you want to create a custom CSS and combine it with a userChrome file.

For me at least, this extension is almost required due to the amount of tabs I have open, and the ability to organize them in collapsible branches is fantastic!

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.