Not as good as Simple Tab Groups, but it's an alternative.

Please add a function to force update favicons for all bookmarks.

Is great with few bugs that if fixed would make it a 5 star.
Bugs:
Tabs merge with other panels sometimes
Shortcuts don't work when sidebar is not displayed
One of my panels lost all tabs once
Moving group to new window causes tabs to fall out of group
Extra Features:
Make snapshots more usable allowing you to rename them, remove and add tabs, organize them, restore or take snapshot of a selection, etc.

Clicking the Add button when all tabs are cleared does not add tabs properly.

Nice! Thanks!

it's a great add-on but I'm having a problem with it.
It doesn't work properly with browser.tabs.closeWindowWithLastTab firefox preference.
I have to deactivate it first.

Please implement

Automatic groups, for example by domain

To close tabs when selecting multiple

Ability to place a new tab button in the top bar

And show an interactive animation line at the bottom of the tabs when loading

Takes some tinkering and getting used to, but helped my quitting my addiction to Arc Browser. Should inform users that you must take snapshots if you want to keep your tabs

good tree better than the firefox one

If I could name and organize the snapshots this extension would be perfect