Best Tree Tabs extension ! And I've tried several !
This one groups the most features I need :
- Tree view
- Tabbed Groups (it would be nice to be able to select background colour of tab like in Opera)
- Pined tabs at top
- Themes (you can create your own one quite easily)

And more !
I also use this one with Opera ;)

Thanks for this great "must have" extension !

After some months of treetabs missing in the sidebar, it has suddenly reappeared, with all 300+ tabs still in order!
I'm so happy about this uber helpful addon getting back on track!
My donation is meant as a big "Thank You!" as well as an incentive to keep on caring about this georgeous baby.

Easily my favourite extension that allows side tabs, as it allows labelling and grouping of tabs into groups.

The problem I describe below the fold is easily fixed by the declopers' suggested workaround, and hopefully will be fixed soon.

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The extension constantly flashes the entire tab sidebar section white every 2 seconds or so - this only started happening today, but I'm not sure why.

Here's a gif of the behaviour - https://gph.is/g/4gpQ7WE

This extension seems to be awesome but unfortunately I can't make it work.

All tabs come back to "Ungrouped" after restarting Firefox and even saving the session previsouly doesn't restore them ok.

The message "Session did not match and will not save! Click here to reload" is appearing too. I'm using Firefox restore session, but checking/unchecking it doesn't seem to help either.

Such a shame, this is everything a tab freak could want (groups, folders, tree structure, load/unload) but without a really strong session management, it makes it hard to trust. There's nothing worst than sorting lots of tabs into groups and folders and tree structures to find out later that you've lost all of that back to a flat structure.

Hope the developer can fix this, it really could be an essential piece of software for those of us who work with lots and lots of tabs.

EDIT: It seems if I check on the "Discard tree structure after browser's restart..." option, click on the reload tree message (and then uncheck the "Discard tree structure after browser's restart..." option again) everything works ok.
Haven't had a single crash or problem since, in any of my profiles (and I have quite a few). So there may be some type of incompatibility with my older extension (tree style tabs).

Awesome extension... I'm donating to the author. Hope he can keep up the good work!!!