There is a enhancement request titled 'Allowing multiple invoice selection for credit card vendor transfer' on the ideas site that is two years old and needs a boost.
https://www11.v1ideas.com/SageE....
If it's of interest to you, please vote. It's also in the KB and it is marked as being reviewed.
I just received another complaint on this today. It's a pain to transfer a dozen invoices to the credit card vendor 1 at a time.