FF Tabs — Tab Superpowers by 53Bits

FF Tabs turns your tab bar into something you can actually navigate.

What it does

Groups every open tab in the current window under its domain, so you can see at a glance where your attention has gone.
Sorts the real tab bar by domain on demand, alphabetical by domain then by title. Pinned tabs stay pinned; tabs inside a Firefox tab group stay in that group and are only reordered within it.
Closes an entire domain in one click from the domain header, so cleaning up ten Google Docs or five Jira tickets is a single action.
Detects tabs pointing at the exact same URL and offers to close all but one — keeping the active tab if it's a duplicate, otherwise the most recently used copy.
Inline search filters your tabs live by page title or domain as you type.
Keyboard-first: Ctrl+Shift+E (Cmd+Shift+E on macOS) opens the popup, ↑/↓ walk the results, Enter jumps to the highlighted tab, Esc clears the search or closes the popup. The shortcut is rebindable under about:addons → Manage Extension Shortcuts.

Privacy
FF Tabs uses only the "tabs" permission and runs entirely inside your browser. It does not read page content, does not talk to any server, does not use analytics, and collects no data.