True, but I use keyboard shortcut cmd T and I would have to learn a new shortcut for this. Cmd T followed by typing url pops up a page where I choose container.
Moreover, I don’t really have tab bar enabled as I use container tabs addon. I don’t really have the (+) button to create new tab.
I had a similar problem and got around this by using couple of add-ons.
I have three containers, work, personal and default. The first addon forces me to choose which container to open to and second let’s me view which tab in which container I have opened.
For the websites which I know I am going to always open in a specific container, I use Firefox’s built in mechanism to force open in specific containers, say JIRA for work. For websites where it is ambiguous, eg gmail for work and personal use, I let the addon handle it. It is convenient enough, as I usually type the URL, but even if you use mouse, the container selection is right there on center of screen.
Ob la di, ob la da - The Beatles.