Two Subinventories with different material accounts how do you stage them

Summary:

Inventory Organization has the need to carry two types of food (normal purchase and USDA) in the warehouse. Each have a separate material account. This is being managed by costing at the Subinventory level. Everything works well until you go to process an order and are forced to the default Subinventory for the Shipping Parameters. How do you keep the material separated during the Subinventory transfer for staging?

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