[coffeekid]

I was looking for this exact setup a couple months back. I found a system that works for me, though not exactly perfect.

You can use the extension "Simple Tab Groups"[1] to automatically open some domains in specific Firefox containers like you described, by assigning a container to a group, and then configuring a domain to always open in that group.

The downside is that not all groups will be visible at a time, and you'll need to first select your previous group before finding the tab you came from. For me, that's an acceptable downside given the advantages it brings.

[1] - https://addons.mozilla.org/en-US/firefox/addon/simple-tab-gr...