Inserting bidirectional subform without display type

Inserting bidirectional subform without display type

I'm trying to create an app with a bidirectional subform that doesn't display the linked field below the subform.
I have two forms.  Main form is "Clients" and subform is "Appointments".  I want to be able to enter appointments in on the clients form and have it be a bidirectional link, but when I do it adds another dropdown field below the Appointments subform.  There is an Application called Employee Management that I'm trying to mimic, but I don't know how to accomplish it.