Related: Multi Account Containers - Same thing as the facebook container but more generi - https://addons.mozilla.org/en-US/firefox/addon/multi-account... Temporary Containers - Same container concept but you can create and destroy them on the fly - https://addons.mozilla.org/en-US/firefox/addon/temporary-con...
After reading about it repeatedly here, I finally tried Multi Account Containers and I'm disappointed. I want to press a button and get site X open in container Y. But as it is, after searching for the container, you then have to search for the website you want to open in it separately. It makes having lots of containers hard, plus there's the risk of accidentally opening sites in your "main container", etc. You have…
When the "always open" setting conflicts with a current container, you get a prompt. If you want to open a specific container, long press the create tab button to get a selection of containers so you can browse to the website manually.
Using multiple accounts works great for me. Clicking on links will open in the same container, opening the website in a specific container is easy, I don't see the blocker here.
I don't know how many containers you intend on using but I don't find the feature problematic at all. Maybe the Tree Style Tabs integration is fixing a problem I don't know about, but it's working great for me.