EDITING Potentials Detail View - Add to Potential to **existing** Case?

EDITING Potentials Detail View - Add to Potential to **existing** Case?

I've noticed that when I'm editing a potential I get all the related entities (like cases, accounts, etc).

I haven't figured out how to associate an existing CASE to an existing POTENTIAL from the potential detail edit screen.  I can add a NEW CASE, but that isn't what I want to do.

My business rules -

- A potential can have many cases, a case may have many potentials (POTENTIAL >--<CASE).

- A potential can be created before a case is created.

- A case can be created before a potential can be created.