Exactly what I needed. Thanks.
If you add the ability to create & choose different groups of persistent pinned tabs, your extension (together with Pin Unpin All) could double up as a very reliable session manager – something which Firefox sorely lacks

Work as a charm. Sometimes I close my main Firefox window with pinned tabs if I have another window Firefox would reopen only the latest closed window without my pinned tabs. With the extension, the first Firefox window opened will load the pinned tab as I wished.

Works flawlessly, and is something I install instantly

Does what it is supposed to do. Nothing more, nothing less.

Works as advertised and was just what I was looking for!