Like, if I had a specific container used for Banking sites, would it be relatively safe from other containers?
Currently, I use Firefox for casual browsing and Chrome for email and financial related sites. But it would be nice to just use Firefox for both. I'm just worried it would be less safe.
I don't want to delete cookies by default (since I don't like to lose my shopping cart due to accidentally closing a tab in a shop I haven't used before), but I certainly would like to be able to ban sites that use cookies in a user-hostile manner from storing cookies permanently.
It would be even better if Mozilla used the voluntary telemetry + manual user feedback to decide which sites benefit from cookies (e.g. web shops), and applied this to everything else (e.g. news sites).
IIUC you want a container to be isolated to a single website, you have to create a container for that website, open the site in that container, and then click the multi-account container tab in the toolbar, and select to option to open this website in that container by default. From then on whenever you open the website, it gets opened in that container by default.