I only use the official "Firefox Multi-Account Containers" (on this browser).
It gives me a menu with choices like "Reopen This Site in..." and "Always Open This Site in..." as well as options to open a new tab in any of the permanent containers or even open new ones.
Tip: if anyone gets confused by a page popping up, saying something like "You asked me to always open this site in, do you still want to " a typical explanation for me was I had set at site to open in a specific container but as part of login procedure it would access another domain for sso, trigger "Always Open This Site in..." for that domain and get confused.
Now that you know this you should probably be able to either avoid it completely by being specific about subdomains or something.
It is not a big thing, just a heads up so nobody gets confused.
It gives me a menu with choices like "Reopen This Site in..." and "Always Open This Site in..." as well as options to open a new tab in any of the permanent containers or even open new ones.
Tip: if anyone gets confused by a page popping up, saying something like "You asked me to always open this site in, do you still want to " a typical explanation for me was I had set at site to open in a specific container but as part of login procedure it would access another domain for sso, trigger "Always Open This Site in..." for that domain and get confused.
Now that you know this you should probably be able to either avoid it completely by being specific about subdomains or something.
It is not a big thing, just a heads up so nobody gets confused.