Settlement to order items is always by cost element

What causes this issue?

Settlement to order items is always by cost element, so there is no
point making entries in the settlement structure.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Do not enter any data for the "Order item" receiver category.

Error message extract from SAP system. Copyright SAP SE.