Creating a child record from a button on the parent form and automatically return back to the parent form after the child has been saved.

I've created "Record ID# of the Root Cause" and made it a summary in (Damage Parts) Table and I have updated the formula in the add button. Everything seems to take, but after creating a root cause record the button does not allow me to edit and does allows me to keep adding records. Is the If statement for the edit/add part of the formula for the button? I have included that as well.