Very nice to have cookies in separate boxes. Noticed a glitch: if I right-click on the New Tab ("+") icon, and select "No Container", nothing happens! Selecting a container name opens a tab in that container. In contrast, long click on "+" icon, and selecting "No Container", opens a tab.

Strongly recommend also getting the Cookie Quick Manager extension for container-aware tasks like deleting cookies from a container, or copying cookies from one to another.