This add on is faster than other vertical tab manager.
Very promising, it just lacks the coloring of the tabs by group for me to adopt it.

Has the most options of any addon I've used!

Very good addon with possibility to hide your tabs that is good in tab-management, beatiful UI, but multi-panel doesn't work properly. Sometimes tabs dissapear from a certain panel, hope you will fix it.

p.s. Is it possible to change ONLY group icon color?
In example, "favicon-placeholder-bg" selector does not fit to this case very well, because it changes other icons aswell, but in order to visually separate tabs this thing could be very useful

p.s.s. Found solution if someone needs. Place it in Style edit.

.Tab[data-parent] .fav .placeholder > svg {
fill: red;
}

But it changes all your data-parent tabs, remember this.

If you need to change color/text-align of your groups in tab panel, try this:

.Tab[data-parent] .title {
color: black;
text-align: center;
}

This extension is EXCELLENT. Much better than the old Tree Style Tabs. Faster, more full of neat features. It's great. I never write reviews, but this one deserves it.

Amazingly intuitive and full-featured tab management. Wonderful integration with other Firefox features, like containers and bookmarks. Full tree structure with everything you'd expect plus unloading, saving sessions (as "snapshots"), and very rich customization support.

Это прекрасное дополнение, которым всегда пользуюсь. Но есть одна существенная проблема. После закрытия браузера слетает группировка вкладок, что очень разочаровывает. Надеюсь, проблему исправят.

nice and simple

Tried it as I saw it suggested. Tree Style Tab user here, but it's not possible to middle click to close a group of tabs. Maybe if this is implemented I might try again. It feels like this extension maybe tries to do too much?

I only used for about an hour, so maybe that's why?