While searching, I found one person asking but never found the idea being discussed.
Is there a reason an option to choose the module isn't available during the assignment creation from the assignment area?
If the assignment is created in a module with the + sign then it is put into the assignment group.
It just seems odd that the page with all the details for creating an assignment doesn't have the dropdown to place it in the module.
Please let me know if this idea exists for voting and I've simply missed it.