Fieldset (Open), add option: Open when populated + Closed when blank

[hiboudev]

Short description of the enhancement

Actually for a single field we can set visibility to: Open when populated + Closed when blank

I'd like to have the same for Fieldset (Open): Open when a child field is populated + Closed when all children fields are blank. So the admin user can see at a glance which information he has filled in.

[elabx]

It would be fantastic to have this option!