Unless I am missing something, I think I have the same question:

 am struggling with thinking there has got to be a way for Quickbooks to quickly turn an estimate into multiple purchase orders to multiple vendors (this before you bill the customer because you cannot bill a customer for something that has not shipped). Why select a preferred vendor for a product if you cannot utilize that information by automatically creating a PO to the vendor.

So in case I am not being clear. Say I have an estimate for a customer who wants a bunch of different books from different publishers. I send them the quote. Then they place the order. I would then send POs to as many as ten different publishers. Obviously, these books are not going to all ship at the same time.

I would like to be able to invoice the customer piecemeal when I find out that the items were shipped to the customer.

It doesn't seem like I can do this, but there has to be a way right?