In Version 13, Doctype layout does not showing list of fieldname , though, before release version 13, we could make another layout based on a doctype. this is visible as per the image. Have anyone used this?
your child table should be blank(there should be no blank row as well) during the selection of document type so it will fetch all fields of the selected document type.
Thanks, Bhavesh! it’s working the way you suggested