Really need to mirror subitems across boards

It sounds like this has been brought up many times before, but this is almost a show stopper for us.

We really need a way to mirror subitems - or be able to put a board in two locations at once as a whole.

I was busy mirroring boards and then realized the subitems were not there! What use is it, then?

Agreed! This would be absolutely crucial for our workflow. Please add this feature! :crossed_fingers: