Hi, Dennis,
just use the full-qualified name of the variable (inputrow.variable). In your example: row4.kundennummer
But I think it won't work because you have to use the index-name of the field instead of the technical dms-name.
customer.kundennummer -> str_customer_kundennummer
The correct index field name can be found in the listtype-definitions:
…rest-ws/service/system/type/name/customer
search-Component-Documentation
https://ecmind.ch/solutions/talend/enaio-redline/red-search/