Payment Request: How can be updated a payment request with a new vendor, once the vendor is created?

Hi, I need some help with this:

In a new payment request, the requester have the option to use a existing supplier  or add a new one.

If  the requester enters the data for a new supplier, (now I know that the supplier has to be created manually), how and who update the request with the new supplier id, once it is register?

Thank you