Model driven app already currently supports this..  you can see from this example

Now this is in the gallery, can we change the status to completed Guido?

https://pcf.gallery/grapesjs-editor/

Only challenge I can see around this is, that stages also must take into account mandatory requirements also before they're allowed to progress.  But I like the concept.

Can this idea be considered closed now ?

Better off binding it to an entity TBH, that way the control isn't context aware.

I had a similar request, but with charts instead of subgrids.  Currently it's not straight forward to inject fetchxml into a model driven chart, and the client doesn't want to fork out for PowerBI (for 5000 users).