Cannot use "setup on child pages" in Containers

Atomik, V. 9.4.1. I cannot use containers in composer templates and use “setup on child pages”. On save, nothing there.
Now that @VisualNotes found how to use predefined css classes for containers, it would great to use containers in composer templates.

There is a github issue on this, which you can add your thoughts to:

Thanks John for mentioning the already existing Github issue.
No thoughts to add, - it’s just not working.