Yes, you can! Go to Accounting>Payables>Invoices. You will see the list of invoices (you can filter for the specific vendor or invoice date).
If it is Unapproved – you can just click on the GL number field and start typing a new GL Number/name.
If it is Approved, you may not be able get to the GL account. But if you Unapprove it, then you can change the GL account (and then you can set it back to Approved)