Question

What registration parameter should be used to force a variant in the Purchase Order document definition?

Answer

The fc_Predefined:VariantId registration parameter can be used to force a variant in the Purchase Order document definition.
 

For the variant to be applied, the parameter needs to be set first and the document needs to be recognized (re-recognized) after. This can be done by assigning the registration parameter value before the Recognition step in the workflow, or by routing the document to the recognition manually or via workflow stage exit routes if the parameter is set after the Recognition stage.