You can add to your client applications, hidden/private fields so that your team still get a dedicated space for any information privately useful to the application (without displaying this information to clients.)
As it says, a hidden/ private line item is not visible on the client interface, it's however visible by third- parties (collaboration feature).
A little locker shows that a line item isn't visible to a client. It's still exported with your application uploads to your Drive or email address.
How to mark a line item as private?
Navigate to the related line item and untick the 'visible by client feature'