Rated 5 out of 5 stars

PLEASE, PLEASE...................... GIVE THE CODE TO SOMEONE AND LET THEM REVIVE "SESSION MANAGER".
Have you seen what is offered now? TERRIBLE APPS to save sessions/tabs.... ONE PAGE/SESSION ONLY. NO multiples of anything. And some say do not try to save more than a few tabs.

HOW I get around it is, go back to FF version 52, am currently trying to find your XPI for FF v52 and don't allow Mozilla to upgrade my browser (despite of the security risks.)
Mozilla is "willy nilly" obsoleting all the GOOD Add-ons like your tab counter (new ones DON'T work all the time) and the best: Session Manager. (here was hoping would reach you as could not find any other contact info).
My way around Mozilla to use SESSION MANAGER: Go back to FF v52 (despite security improvements). AM TRYING TO FIND the MSI, your version of Session Manager for FF v52 and avoid Mozilla upgrading my FF.

PLEASE FIX AND I WILL PAY TO USE IT.

This review is for a previous version of the add-on (0.8.1.13). 

Rated 3 out of 5 stars

Firefox calls the browser a WINDOW I think, and the URL box a TAB.
But this add-on uses the words: Window and SESSION, BUT, which is which?
I don't know if I need to save a WINDOW or SESSION or what will be lost and what is saved.

This review is for a previous version of the add-on (0.8.1.9).