As my team works more and more in populous domain models, we’re finding it harder to keep things grouped and easily readable. Not to mention, easily findable. This may be a reach, but it would be really interesting if there was a sub-domain model feature where you could group several entities together and place them inside a container, and only that container is shown when the sub-domain model is minimized. You could either click to expand or open it as a different tab to see and edit what’s inside, but it’d probably be a hassle moving things in and out of it with the latter option.
But I like Rob’s suggestion better.
Wouldn’t you just create another module if you want to group your entities that need to be grouped?
In my apps I usually create a few modules and there you can just add your relevant entities and create associations to other modules if needed (try to minimize because it would make your modules less independant)
In https://forum.mendix.com/link/ideas/2154 I made suggestions to improve Domain model readability, not sure if that would help in your case?