Hi HM Yiu
The feature is not available the ability to configure the Form Recognizer model to return values with a 'X' next to them is not a built-in feature of the service. The Form Recognizer model typically extracts key-value pairs from documents, and if a field is skipped or not recognized, it won't return a value for that field.
So as of now, I guess this is not possible in the default form recognizer.
If this helps kindly accept the answer thanks much.