The 504 Participation Fee Amount can be tracked within the Closing Requirements > Servicing Agreement menu towards the bottom of the page.  It is automatically calculated for you based on the Senior Lender Amount and is not editable.  You can input the Amount Received and run a report against received/outstanding fees.

The Servicing Agent Agreement (SBA Form 1506) also populates  section 2.b.c. from the drop-down below labeled Fee is.