Tree Tabs от kroppy

You can manage your tabs in a tree structure with folders and groups.

Some of many features:
- Drag&drop tabs to arrange your tabs in a tree structure
- Multi selection with Ctrl+click, Shift+Click
- Create groups and folders
- Save and Import groups or sessions
- Search tabs using search tool

Shortcut keys:
- F1 to toggle Tree Tabs sidebar
- Ctrl+a select all (works on one level, where active tab is)
- Ctrl+i invert selection (can conflict with Firefox internal shrotcuts)
- Ctrl+w to close entire tree

Get more themes here: https://goo.gl/UtQ5vG

Incompatible extensions that will cause loss of Trees structure:
MySessions
Session Sync
Tab Session Manager
Tab Save & Restore
Tab Unloader (WebExtension)
Tab Saver
MySessions
Session Resurrection
Tab Suspender (memory saver)

Extensions that can cause other issues:
NoScript will block background script

Any extension that colorize tabs will not affect Tree Tabs tabs. For example:
VivaldiFox
Tab Colors