Pin Unpin Tab от Jayesh Bhoot

Note that double-click on a tab (active or not) to pin/unpin is not going to be possible due to the limitations of the WebExtensions technology. Only Mozilla can fix it, not me. Look here and here for more details. Instead, use the (arguably) more efficient alternative - a long left click anywhere on the webpage, which is also customizable in the add-on preferences.

Pin Unpin Tab is a Firefox WebExtension to pin or unpin a tab by
- a long left mouse click anywhere on the webpage (an arguably more efficient alternative to the no longer possible double-click on tab). This option can be enabled or disabled on the add-on's preferences page. The minimum duration to hold down the click also can be set. This approach will not work on AMO webpages and the Firefox pages (eg., about:addons).
- a keyboard shortcut Alt-P (Ctrl-Shift-P on macOS), which Firefox allows to customize. See the guide at: https://github.com/jyshb/pin-unpin-tab/issues/17
- a click on the pin icon on browser toolbar. The icon gels well with the default light and dark themes

Credits
Icons made by Smashicons from www.flaticon.com is licensed by CC 3.0 BY