I was looking for the ability to sort my open tabs via a firefox add-on/extension. I found this. Sorting isn't listed as a feature, but Tree Tabs effectively allows this.
Two Steps: I search and put the matched tabs in a group.
This tool seems better than the ones that just offer sorting. Just started using it today.

You can add folders and tab groups, which makes this addon a solid solution for organizing your tabs. Improvement can be won on displaying children in the trees. It is not really clear which ones are child elements of a parent element in the tree. The distance is not big enough. Maybe the use of colours can be a solution for that.

Tab trees no longer break on startup, yay!

However I have the same issue as the last reviewer. After a while new tabs won't display in the tree until you disable then re-enable tree tabs(or firefox).

1.7.6 on latest official firefox release

There was a bug.
Version 1.7.6
1. When adding a new tab, the tab is added, but it is not displayed.
When restarted, it is added to the bottom of the group.
The occurrence condition is unknown.
There is no problem immediately after rebooting, but it will occur again after a while.
I am setting to add all tabs as child tabs.

2. When tab group was imported, the tab structure was broken.
Also, "Rearranging tabs and folders" does not end.
It was not possible to open it by clicking the tab, and when restarted the tab had disappeared.
After importing it back to v1.4, it worked.

!
Oh, there was such a place.
I will report it when I find a bug in the future.
Thank you for maintenance.

Tree Tabs is easy to use, simple, but really useful when you need to manage a lot of tabs.

You can organize tabs in a tree structure in the sidebar. Fold it or unfold it. Navigation of tabs has made simple.

Wow, this is VERY promising and I'm already using it full time. If the bugs get ironed out this could be one of the most popular extensions for firefox.

I've been using this for quite a few months, and the developer has added some very nice features during that time. Organisation of tabs is a breeze with this thing.

I can select tabs without loading them, put tabs into general organisational groups and trees under each other, close and move lots of tabs at once, and so on. The tabs are also displayed pretty compactly by default, and additional information (such as whether or not a tab is loaded) is well conveyed. A number of these features cannot be found in some of the more well known tree-like tab extensions, which is why I use this one.

.

Would it be possible by an option to change this shortcut key ? *Ctrl+F2 to toggle Tree Tabs sidebar*
I would love to use Ctrl + Q, if possible, in a future upgrade consider for this option :)
Thank you very much, this extension is wonderful!

I FOUND IT!!
Now IMPORT can open!!
THANKS A LOT!!!

Awesome add on ! Seems to be a great successor for tabkit 2 !

Some ideas and remarks :

Color tabs when a child tab is opened , I mean that each tree could be colored in a different color : it's very useful ! (a click on a link opens a new tab in the same color of the current parent tab, the main parent tab is colored only when a child tab is opened) .

Highlight tabs in a special color for links opened in a new tab but the tab haven't been opened/clicked/viewed.

You could also add a checkbox for "mousewheel scroll on the last tab allow to return to the first one".

Shift + mouse scrool to switch between groups

A keyboard shortcut to close a tree could be nice too ;)

Add a tutorial on the add-on web page to explain how to remove the original horizontal tab bar from firefox.

Thanks for the work on this add-on !

The only extension seamless combining tree style, folders and groups. Also theme customization is amazing.

Great add-on. I'm still not a big fan of horizontal tabs but I'm sticking with it until a real a «Tab Groups» alternative comes about. The ones that exists have many problems that need fixing.

Of the "tree tab" add-ons I've tried this one has the most feature sets I'm interested in. Most important >Tab Grouping... Tree hierarchy, Tab Unloading, Searching, Sorting are just really nice features. The latest version can now 'hide' tabs when you switch groups without closing them so now it even more useful. You can switch tab groups and then hide the sidebar if your strapped for screen real-estate.

After «Tab Groups» etc. died because of WebExtensions I had to find some good alternative and settled with this one. It is so feature rich that I consider contributing to this great Tab Manager

Cannot live without it, but just today it started losing the grouping of 200+ tabs every time i restart firefox. I can provide you more details about the problem if you want, I need it to get solved because grouping it's the main reason i use this extension.
Thank you

Liking this so far, lots of nice features, but haven't tried them all yet. The groups feature is a welcome addition. I could say this is an addon that could replace a bunch of other ones I have (session saver, tab groups) if the tab group import and expert, and the tab session import and export worked for me, at least it doesn't right now on my Mac, High Sierra. If it works on Windows that'll do me as that's my main power user machine anyway.

Issue I am having on the Mac is that the export saves it as a csv, and importing looks for *.tt_group or *tt_session - renaming the extension from csv to the correct one it's looking for, or just trying to load in the csv - both methods result in nothing happening.

Also the search feature would be better if it just showed the matching tabs rather than highlighting them. But personally not a feature I can see myself using much as I'd just search using the address bar.

Good effort though, switched from Tree Style Tabs as half the time the tab side pane would just load endlessly and never complete.

EDIT- the import/export works well on Windows, but it crashes my Firefox A LOT :( weird, as I don't have this problem on my Mac. It will hog maybe around 50-60% of my CPU :/ disabled for now, but I really want to re-enable it later down the line, I really want this addon to do well.

Much less buggy than Tree Style Tabs. Also I love the search tabs feature and it seems to be more lightweight and more responsive than TST