The concept is great and the best solution to managing multiple accounts and containing them into their own separate bubble. But I'm experiencing a significant performance decrease when using this extension, especially on video hosting and streaming sites such as YouTube. This extension's gonna need a lot of optimization.

nice

it works great BUT I can only partially access the 'Manage Containers' screen to customize or edit existing container or add a new one, the 'Save' button is not visible. The "manage container' button on the previous screen is barely visible.

This does not work for me anymore, does not open the urls in the new containers as it should. Something has been broken for a few firefox versions now.

Still no manual adding of URL's !
Workaround here:
https://github.com/mozilla/multi-account-containers/pull/2114#issuecomment-1004056712

Good tool for security and dealing with numerous accounts when performing administration for a group of clients.

please add a similar extension for managing profiles , not for individual tabs but whole browser, like on chromium based browser

Just new for me, but it seems interesting.