Helps you separate accounts and groups of accounts, even allows you to always open a site in a specific container

This is the main reason why I still use Firefox! Works perfectly (especially if you have to login to multiple O365 accounts, which can be brutal)

Love this add-on. It's been great with my work to keep certain sites separated from each other. I use multiple Office 365 accounts a lot for example and using these helps with the admin login persistence issues. Also helps isolate junk sites that could be intrusive.

Excellent.
Though at the early time it might be confusing for new users.