Current behavior: When there's a default container for a website and that website is opened, Firefox asks if the user wants to open that website in the current container or the default one.
Problem: When there are multiple containers that the user uses to open a website frequently, if the one that the user wants to use at that moment is not suggested, they have two options:
Suggestion: allow setting multiple containers as default and then show buttons for each one. Some ideas:
The first suggestion would be something like: