I installed the Multi-Account Container Extension and it worked fine until I added the fifth container. Now the window does not shot the Manage Container button at the bottom, and I can not add anymore containers. I've removed the extension, and restarted Firefox, re-installed the extension, and still the issue remains. I do not know where to go from here. And if this feature is so difficult to use, or has bugs that I can get corrected so I can use the feature. I will remove it and not even waste my time. I've been using Firefox for over 20 years, but I am not going to continue if the extensions or other features fail to live up to the standards I think Firefox should hold. I tried taking a screenshot of coping the extension window but could not figure out how to do that. So suffice with the fact that the Manage Account or container button that was at the bottom of the window no longer is there.