[solarkraft]

I don't know how you can deal with just vertical tabs. Sidebery (FF extension) offers tree tabs and it's really cool.

[toastal]

I thought Tree Style Tab was the preferred Fx add-on.

[solarkraft]

I prefer Sidebery because it feels faster, more reliable (TST seems to struggle much harder with a higher number) and has a prettier default theme.

I think it also has many more config options, but I'm quite happy with the defaults.