How to reschedule a date for drop ship sales order or update Ship To Address when PO exists?
Per Doc ID 2231220.1 it is not possible to reschedule lines for drop ship orders.
This is on the basis that Fusion Procurement doesn't allow open drop ship requisitions to be updated and consequently Order Management doesn't allow changes during that stage. Further, there are seeded constraints that prevent update and cancel of a sales order line when an open PO exists. This is intended to alleviate the possibility of requesting a change on a PO which the supplier may reject.
However there is seeded functionality in OM Setup and Maintenance in Task 'Manage Order Attributes That Identify Change', task type - DOO_PROCUREMENT, that includes a list of predefined attributes which do pass revisions from drop ship sales order to PO's (refer -