Assign Payment to Invoice in Invoice View

Currently if user opens an invoice they have option to make a payment, but are not made aware if the contact has unassigned payments sitting against their accounts, nor can they then assign that payment to the invoice for payment.

If the user knows there is an unassigned payment they can go to that payment and then assign an invoice to it, but this is a bit backwards in the normal process of making payments and requires users to stay on top of what payments are unassigned for what contacts.