I'm testing this add-on on a firefox 85.0.2 (64bit) and it seems it's not working at all.

As others have said after installation it shows 53 overdue tasks which are nowhere to be seen. Furthermore if you try to create a new project you can not click confirm or press return to actually create the project. Therefore this add-on seems to be non-functional.

Maybe it used to work on an older FF version but currently it does not work. The Add-on may need some maintenance / update work.

It doesn't work. It always says there're 53 (?🤔) overdue tasks even before adding any and it loses any tasks you add immediately after its popup window closes.