Make it Zen от G.R.Dias

Zen Browser-inspired touches for Firefox: copy the tab URL with Ctrl+Shift+C, preview links in a Glance panel with Alt+click, and control whatever is playing in your tabs from a sidebar. Collects no data.

Copy tab URL
Ctrl+Shift+C copies the active tab's URL and shows a small notice at the top of the page. On pages where extensions can't run (about:, addons.mozilla.org) the toolbar icon shows a ✓ instead.
Note: Ctrl+Shift+C is also Firefox's default shortcut for the Inspector, and Firefox may keep it for itself. If the shortcut doesn't work, either change the Inspector shortcut in Firefox's Keyboard Shortcuts settings, or give Make it Zen a different shortcut in about:addons → gear icon → Manage Extension Shortcuts.

Glance
Alt+click a link to preview it in an overlay on top of the page, with a rounded header and an "open in new tab" button. Esc, the ✕ button or a click outside closes it. If a site doesn't allow previews, a notice with a 5-second countdown appears and the link opens in a new tab.

Players in the sidebar
See every tab that is playing audio or video: title, artist or channel, artwork, the site's favicon, play/pause, timeline, volume and mute. Click the title to jump to the tab. Previous/next work on YouTube, YouTube Music and Spotify Web. Colors follow your Firefox theme, and long titles scroll in a loop. Settings live in a collapsible block at the bottom of the panel.

Back shortcut
Alt+Left closes Glance, or a tab that was just opened from another one, and returns you to the previous tab. To use your mouse's Back button, map it to Alt+Left in your mouse software.

Privacy
The extension doesn't collect, store outside your browser, or send any data. Everything happens locally. Permissions are used only for the features above.

Disclaimer
Make it Zen is an independent project. It is not affiliated with, associated with, authorized by or endorsed by Zen Browser or Mozilla. Product names and trademarks mentioned belong to their respective owners. Open source, CC0.