Hi Hiwa.
I don’t know I get you right and I don’t know what you will do after mapping.
But if you declare the <Row> as a Attribute of the Element <ColumnX> so you can fill it just if the source is filled otherwise it will not seen in the output xml file. But I’m not sure if this helps in your scenario. Also I’m not sure if it exist a property for your issue in the destination element.
Hope it helps or give some other ideas.
Wolfgang