on some computer i don't succed to see icon in extension bar...so it's not easy to use. even if i have it's icon on my own computer ! i don't know how to solve this issue... this is the only reason why i give 4 stars because when icon is here, it merit 5 . Thank for your answer...i corrected to 5 stars. 👍
You have to access the icon using the "Extensions" button on the toolbar (puzzle piece icon). In its menu you'll find "Undo Close Tab" and if you like, you can select "Pin to Toolbar" from the menu there.
This is not at all convenient but this is the way Mozilla enforces for Add-ons.
