Was looking for this for ages.
There's always space for improvement (bookmarking a tree w a single bookmark, hiding top tabs...), hope they/you keep up improving it. But it is best I've seen managing tabs - and I've tried several. Congrats!

awesome add-on with good information and howto make it better

PRO--
Vertical tabs provided by Tree Style Tabs is a wonderful idea. Despite Mozilla's rush to Quantum, at least Piror has provided a version that works (after a fashion) with FF Quantum

CONS--
1. Many of us who use Tree Style Tabs regularly have a great need for its companion extension, "Open Link in New (Tree Style) Tab". OLNT is available for pre-Quantum FF, and works fine, but is not available (yet?) for Quantum.

2. Under pre-Quantum FF, we could create a bookmark of all open TST tabs. Under Quantum, however, we are told Quantum has a bug which prevents our creating a bookmark without prior FF permissions, and are told to use the TST toolbar button to grant ourselves permission to create bookmarks. However, the toolbar button has no explicit control to grant permission, so we still cannot create a FF bookmark of TST vertical tabs.

3. Many of us expected that when we installed the Quantum version of TST, the top-most, horizontal tab bar would disappear, as it always did in pre-Quantum FF. But no-- the horizontal tab bar remains, for some inexplicable reason.

Very good idea but there are some issues with recognizing "pending" tabs. They should be red according to my settings (and it already worked for a short time) but they just keep the style of regular tabs. With over 300 open tabs, this is unfortunately not funny if you don't know which tabs are to be visited yet. With regular CSS and (userChrome) and FF tabs it works like a charm though.

When it works it's cool, but sometimes it just keeps loading and nothing happens! Now I have 3 tabs open and its been 25 minutes, still it is showing the loading animation, 25 minutes to load 3 tabs is not right. Very nice add-on but very buggy. The only solution is to close the tree style tab sidebar and then again click "show sidebars". Then it works perfectly. Hope its updated soon.

非常不错的主意！！！！当标签页多起来时，看着原生的标签管理 你会忘了你到底打开了些什么，一团糟。现在一切都好起来了。

This extension is the main reason I use Firefox.

One request: I wish settings/custom CSS would use Firefox Sync.

I have been using it since a long time ago.
However, we frequently lose tab positions in various situations, such as when restarting or restoring with a session manager.
Moreover, I also forget the hierarchy.
This is fatal.

This extension bugs out a lot, forgetting the positions or tabs between plugin crashes and even between F1 sidebar toggle presses. I LOVE it when it works, but I HATE it when it doesn't, as it takes at least 5 minutes to fix the mess it creates when it breaks. (All the tabs are randomly ordered, parents forgotten, some tabs are even missing from the tree altogether and exist as "ghost" tabs between ones actually in the tree!)

This is an invaluable extension, seriously! It's one of my biggest practical reasons for using Firefox. However I have noticed that the tab context menu doesn't always show options that should be added by other extensions, which is quite annoying. Oh well. This is a fantastic extension still and I'm grateful it's being updated :D

This extension is one of the reason I keep using Firefox. Makes it easy to use hundreds of tabs. Has all the functions I need and is still in very active development.

Great for organizing tabs. Now this extension and the ones like session managers and tab groups (Panorama) need to integrate with it.

Brilliant idea, poor solution. Unstable a buggy in all versions.

A necessary extension to Firefox. The main reason I use Firefox is for vertical tabs, and this works very very well.

I had a recent problem with TST not initializing, but removing and re-adding the extension fix me right up.