Suggestion: I wish if there was not so many visual affects on the tab bar. Meaning, when I switch from a container to another there is so much of visual mess. Additionally, sometimes the tab that moves to a different position probably because of my other tabs, so I suggest to fix this.
Note to creator: Here are my desired additional features (that the old MultiFox had):
Feature A. Step 1. Click once on Multi-Container button, list of profiles shows up. Step 2. Click on desired profile, new tab opens with current URL but with selected profile.
(In contrast, the Context Plus add-on requires that I (i) right-click on the tab; (ii) move mouse cursor down to "Move to Context" and wait for further drop-down window to appear; (iii) then "Ctrl+Click" desired profile.)
Feature B. The ability to rapidly open the same URL across multiple profiles. With MultiFox I could just click the MultiFox button, then click-click-click-click across all my different profiles and open up multiple tabs with the same URL, but each with a different selected profile.
(In contrast, the Context Plus add-on closes the earlier drop-down windows and immediately brings me to the new tab once I click on one profile.)
(The above was also posted at https://github.com/mozilla/multi-account-containers/issues/311.)
I upgraded to FireFox 54 a few days ago and it broke a plugin (called Multifox) that I depended on for my daily workflow. Someone suggested that I try Containers as an alternative but I found it useless until installing your add-on.