To confirm, is there a way to do a single ITR that pulls from multiple purchase orders? For example, when a vendor delivers one container that includes multiple purchase orders?

No you can only link a receipt to one purchase order. The inbound shipment feature will allow you to track and recieve multiple POs at once, but it wills till post an individual receipt for each PO, but the inbound shipment kind of "collects" everything under it so its a little easier to process transactions

ah...ok, that feature sounds familiar...thank you!