Correcting error : Linking PO and PI


I made an error when I posted a transaction.

Typically I use …
PO → (advance payment : if any) → PI → payment

In this case there was no advance payment …
PO → PI → payment.

I made an error, so I have …

PO … PI <-linked-> payment

PO not linked

Is there a way to correct this ?

The rather simply way that I thought was , to simply make a “comment-entry”
stating the PI number and simply mark the PO as CLOSED.

I was hoping there is a proper way of making the link ?