The best implementation of vertical tabs you will find ANYWHERE, extremely smooth, feature-rich, actively developed, and customizable with tons of setting options!

To those using the review system to report bugs: report them on Github.

A lot of features and options ... but regularly, my tabs lose their group membership (1 tab, 10 tabs, or 40 tabs or more ... I haven't found any obvious logic while issues occur).
Group reliability is the 1th expected feature before coloring or any customization. As a result, experience or feeling is mixed.
Important: no sync enabled, no other conflicting add-on.

Essential if you regularly have more than 10 tabs

thank you

It's literally perfect

Works well, until it doesnt

Then you'll lose any tab you had open and have no way find out what they where apparently

works perfectly and so customizable so fits my very specific workflow :)

Unlike TST; Handles tab groups and tab colour. Panels adds another level of organization.

Lost a star for: 1) Not providing for increased indent on child tabs (group tab colour, inherited by child tabs serves the same visual purpose; which doesn't apply when you are actively accessing children of multiple search tabs) [settings, style editor, tabs, indent=25,on]. 2) The inability to show bookmarks at the same time ala TST. (but there is an icon {bottom middle} to bring up a book mark sub-panel).

There is no obvious way to show bookmarks in the sidebar. I searched for about 10 minutes and could not find an option to show the bookmarks. All I got in the sidebar was tabs—which I definitely did not want to show in my sidebar. Moreover, even it I were able to located the setting to install my bookmarks in the sidebar, I do not believe I would be able to with one click open a sidebar with my bookmarks showing. Apparently I would have had to click on the Firefox sidebar icon, then to click on the Sidebery icon. That's not acceptable. Is it unreasonable to be able to make one click to show a sidebar of bookmarks?

I've been using this for a few days and it's been exactly what I needed so far. I'm one of those people who opens way too many tabs when researching things, figuring I'll do the slower sorting and bookmarking later when I'm pressed for time. Sidebery lets me manage any number of tabs better than most of the add-ons I've tried. Give it some time to really adjust to the change. Loads of configurable options to allow me to fit it pretty much perfectly to my use profile. It appears to also be managing memory better than just overloading the regular tab bar but I'll need to track that longer term.