[thworp]

Tree style tabs is more stable and performant but also has a few nice addons (TST Colored Tabs being one of my favs). Sideberry can be infinitely customized but I found it to be extremely slow with 100+ tabs across multiple windows.

[quesera]

5233 Sidebery tabs here, in a single window/profile. Multiple Sidebery "panels". I am simultaneously running a few other Firefox instances with their own Sidebery extensions and at least hundreds of tabs each.

I will not defend this use model to any skeptics, but FWIW I have no performance issues!

Sidebery lets you set colors on tabs explicitly, or by pattern. I use this sparingly but it's very useful when I do.