Payment Entry Deductions with a Party/Party Type Account

I need to add deductions in payment entry against an account that is payable, I managed to add the Party and part Type to deductions table and select them, but on submit I get an error that party and party type are not set.

I need to know how to set them to the G/L upon submission, (Very limited coding experience, so handling it with minimum coding would be appreciated.)

Use case of paying commission to partner based on customer payment. We can write a simple script to check if partner for customer or sales invoice and do offsetting entries in the Payment Entry deduction child table. The entries would be to cost account and payable account for partner. Need to define party when using payable account and the Payment Entry deduction child table does not currently allow.

Presume it is not as simple as customizing child table form to have a party field which is linked?