It lets you join tabs into a group, where you can add tabs to the group, remove tabs, and expand and collapse groups all in the regular tab bar without any other menus.
I prefer Sidebery to Tree Style Tab. I've used both quite a bit, but I really like Sidebery's snapshot option to save and reload snapshots of your session, either manually or on a schedule.
I don't know how Chrome does it but there is Tree Style Tab that let's you group tabs and collapse them.
https://addons.mozilla.org/en-US/firefox/addon/tree-style-tab/
Chrome does it like this:
It lets you join tabs into a group, where you can add tabs to the group, remove tabs, and expand and collapse groups all in the regular tab bar without any other menus.
I prefer Sidebery to Tree Style Tab. I've used both quite a bit, but I really like Sidebery's snapshot option to save and reload snapshots of your session, either manually or on a schedule.