Tab Session Manager basically saves copy of your windows or groups of windows whenever you close them, or on demand, for you to summon back whenever you need them. It's a really great add-on for people with tons of tabs and windows! The interface is a bit aggressive with its popup asking for donations, but it's fine otherwise!

My only request is that I'd massively prefer a sync option with my Firefox account over the provided Google drive option. In corporate environments, it's not always an option to use Google services! Changing this would get my review up to five stars.