How to make PO line DFF Mandatory in Redwood PO Page

Summary: How to make the PO line DFF Mandatory in Redwood page

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Trying to make DFF at PO line level to mandatory for a specific document type in redwood page as below. But its not working as expected

Version (include the version you are using, if applicable): 26A

Code Snippet (add any code snippets that support your topic, if applicable):