Typical issue of a multiprovider-solution where the involved infroprovider are not on the same level of detail (1-N)
Personally not a big fan of the constant selection solution as it is not very dynamic (since it is dependent on the object you put in the drilldown or selection).
One solutiuon might be to bring the "1" level data to the "N" leven in a new (physical) infoprovider through ETL. The biggest issue of this solution (technically) is KF's that you have one the "1" level, since they will be duplicated. Can be solved via exception aggregation (on the shipment nr in your example), but this can be quite expensive from a performance POV.
Other option might be a joining the infocubes in an infoset (so you get a join instead of a union), but personally never used this approach tbh.