Undo Closed Tab Button add-on allows you to undo closed tabs via a toolbar popup.
To work with this addon, simply open the toolbar popup and click on the desired tab to open. By default, 25 items are shown in the popup, but you can change this from the options page. Each item has a title and a fav-icon (if available). There is also a button in the UI (bottom-left corner) to open all closed tabs.
If you have a feature request or found a bug to report, please fill the bug report form on the add-on's homepage (https://mybrowseraddon.com/undo.html).