Hi Patrick,
1) Have a look on the below blog , Even i tried the same so eventually went for this approach.
SAP HANA: Handling Dynamic Select Column List and Multiple values in input parameter
Graphical approach works but with the projection:
Using Multiple Values in Input parameter for filtering in Graphical Calculation View
2) Also try APPLY_FILTER as mentioned above by sagar.
Regards,
Krishna Tangudu