YATS - Yet Another Tab System von Robert F.P. Ludwick

When installed in Firefox, YATS adds a quick tab switcher you can open from the
toolbar or a keyboard shortcut. Type to fuzzy-search across your tabs and related
sources, then press Enter or click a result to go there.

• Open tabs — Search all open tabs across windows, including tab group names.
  Results are tagged with colored badges for the source window (when multiple
  windows are open) and tab group (using the group's actual color).
• Closed tabs — Optionally include recently closed tabs (session restore).
• History — Optionally search browsing history as you type.
• Fuzzy matching — Subsequence matching with scoring (consecutive characters,
  word boundaries, and cross-field matches like group + title).
• Smart tab focus — Optionally return to the previously active tab when you
  close the current one (MRU behavior).
• Session hygiene — The switcher popup is kept out of “reopen closed tab” history

Actions

• Open / close switcher: Ctrl+Shift+Space (macOS: Control+Shift+Space)
• Navigate results: ↑ / ↓
• Activate selection: Enter or click
• Close switcher: Esc

You can also click the YATS toolbar icon. To change the shortcut, open
about:addons, use the gear menu, and choose Manage Extension Shortcuts.

Settings

Open the gear button in the switcher footer to configure:

• Which sources to search (open tabs, closed tabs, history)
• Whether closing the active tab should focus the last-open tab

Settings are stored in browser.storage.local and persist across browser restarts.