Add a new List Fields in WFR generated XML file

Hello Experts,

I need to add a new field in WFR generated xml file like vatInclusiveFlag which hold the value yes if vat value is present in invoice else it will have a value No.

Please advise what are the steps I need to follow as when I'm following the DOC ID 1268783.1 to add a new Field getting confused how I will train the Field and how I will determine the Field value to yes/No.

please provide some Guidance.

Thanks

Sanjeev