If you have set up a payment ID on a creditor card, it is nice to be able to see it and check it in the Physical Vouchers (inbox) before transferring to the journal for posting and payment.
The payment ID field in the physical voucher (inbox) is always empty so that the user has the opportunity to enter another payment ID here. If you would rather see the payment ID on the creditor card you will need to get it by clicking on the 'Layout' button in the local menu ribbon and selecting 'Other fields.
Select 'Creditor/Payment ID'. Click on the large arrow and click on 'Finish'. Remember to save this layout using the layout button once again and 'save layout. An example is given in this Danish video in minute 26.