Hi Robert,
it is possible, but let me to understand your requirement, so you need a new Field in selection screen which exist in SAP-Table ( so you have added it )
but you can add this field in KNA1 and not in KNVP.
could you please take a look at this logical database
So, if you have zfield in this structure, so it could be added , but others table, how can you show it in dynamic selection,
According to my knowledge , it is not possible.
Regards
Ibrahim