Is there a way to view a purchase order number in the line items of a purchase order?

For some context, I have a vendor that partially bills multiple purchase orders on any given invoice. When billing all the purchase orders at once, obviously all the open items from all the purchase orders show up and it would make it much easier to know which line items to delete, if I could confirm what purchase order each line comes from.

I know the items show up in order of purchase order number, but when going through over 10 purchase orders with anywhere from 5-25 items, some of which are the same items and may or may not be in the full amount of the purchase order quantities, it gets a little difficult to weed through.

I tried to customize the form and checked off “PO Line ID” under Sublist Fields, but nothing ever populates in that column.