Collapsible AB Container

[sokratesagogo]

We use the AB Container block to create and organise some quite complex layouts - it's a great block, thanks!

It would be really great if the AB Container block, and the blocks it contains could be collaped like the edit boxes in the ye older Classic editor screen

The Classic editor screen could get quite busy, and offered a way to collapse any of the editor boxes to make things slightly less cluttered and easier to manage, especially on smaller screens.