I think it would be a good enhancement if the popup to edit an entity had a tab so that the foreign keys defined for the entity would be visible (and hopefully editable).
You could think of it as another path to get to the “Relationship Properties” that exist for this entity where this entity was the child table.
The modeler that I’m most familar with (Oracle JDeveloper) does this and it is very convenient. In fact that produce does not have a separate “Relationship Properties” dialog, but when you double click the relationship line it brings up the “Edit Table” dialog positioned to the “Foreign Key” section and has the particular foreign key that I clicked on selected.
Just a thought.