This a really useful extension for working with multiple cloud service accounts (e.g. AWS assumes a global session, GCP theoretically supports multiple logins but it's in the usual Google NOQA zone where many things break) but there's a really important limitation to know about: the container configuration isn't synchronized with your account. This means that if anything reset your Firefox profile (like that bug they had last year) or if you use multiple computers, you'll be spending a lot of time duplicating the configuration:
See https://github.com/mozilla/multi-account-containers/issues/3...