This is very useful. I hide the top tab bar with a userChrome hack and just use this addon. I like the compactness of the tab bar.
What I miss is support for container tabs - VTR doesn't show the container color and doesn't have the menu to move tabs into containers.

Just installed it and Wow! It is reacting to clicks much faster than Tree Style Tabs. Does not seem to require too broad permissions. Does not come with attempt to show tabs in tree which I anyway disabled whenever I could. Just seems to do well what it should do.
I hope that Firefox stops leaking memory like crazy as it used to do with TST.

I wish it also had bright color theme with less intense colors.

I just started using VTR today and find it clean, unobtrusive and easy to use and works well with the native Firefox sidebar. I think it will become my fave tabs manager very quickly.

Fellow dev here. Nice work - this is great.

Great addition. One of the enhancements you can make to your browsers that makes you go "Why wasn't it always like this?".

One significant improvement would be to allow users to reverse order the list. I open a lot of tabs and tended to work from right back to left. In vertical tabs, this means I am working from bottom to top and I would much prefer to work from top to bottom. Please consider allowing users to reverse the order of the list!

Apart from that, works great 5*

Really clean & useful tab's plugin. Just one litle issue, we cant use it to disable main tab's bar. I know you can't do it with a plugin since firefox 57 but it's sad ;(