From Dynamics Explorer we have info on more complicated AP application.
Scenario I often see this request via support so thought I’d document it on my blog. The question varies however it usually goes something like this: “I’ve accidentally applied an invoice to a Payment and now I need to unapply this however when I select the Payment in the “Transactions > Purchasing > Apply Payables…
— Read on thedynamicsexplorer.com/2020/06/10/dynamics-gp-how-to-unapply-a-payables-invoice-in-history-thats-applied-to-a-open-credit-document/