The groupbox widget can with a few improvements can be a lot more useful as a container for drill down information.
Examples below in the screenshot which shows 3 levels of drill down with Group boxes that act as Master-Detail tables ( A > B > C )
There is only 1 improvement needed : Allow Groupbox Header to contain other widgets.
“It's not toooo difficult, but purists might argue that client side things dont belong in the domain model.”
Exactly my point too. Any hack or workaround is just that, replacing a pretty obvious gap in functionality with domain model based show/hide flags.
My point remains the same – drill down tables, expand collapse UI elements like groupbox need to be standard functionality. A lot of app designs depend on basic features like these to “group” / show/hide releated information and provide context for the grouped data.
Groupbox with header – by the way is now a marketplace addon widget (but limited by features needed) :Mendix Marketplace
I dont think you'd want to mis-use groupboxes for this.
I think what you might want to do is have a button that toggles a specific class on or off.
You can currently do this with dynamic classes.
It's not toooo difficult, but purists might argue that client side things dont belong in the domain model.