It’s a little known secret, but actually, with manual journal entries and with most user interfaces in SAP, you can actually overwrite the values that SAP proposes.
SAP will dutifully propose the exchange rate, the payment terms, the due date, the document type,… all kinds of useful parameters.
However, with enough access, you can change these values during your input.
So a 10USD invoice in local reporting currency can become a 10000 EUR invoice in payment currency.