We looked previously at Vendor and Customer Combiner moving into GP proper from PSTL. Now David Musgrave has some help around this for Developers: Microsoft Dynamics GP 2013 Service Pack 2 moves the Vendor and Customer Combiner & Modifier into core code
Developers: Microsoft Dynamics GP 2013 Service Pack 2 moves the Vendor and Customer Combiner & Modifier into core code
Payables & ReceivablesDevelopment & IntegrationGP 2013
Archived post from 2013. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.