If a customer should order a product marked as Preorder, how can we ship the other products without charging for the preordered items and still maintain the preorder status to that item so we can charge & ship when it does become available?
You will only capture the dollar amount for the items you are shipping. The resulting billing status will Paid-Partial. You can then split the shipment to create shipping labels for the items that are shipping right away. The resulting order status will be Shipped-Partial.