Currently TestStand does not support the automatic/internal conversion of arrays of containers to arrays of structures, and vice versa.
The only conversion close to this is the conversion of container to structure, and vice versa. This is upported when container and structure are used as a function argument when the function is called using the DLL Flexible Prototype adapter. It is a feature of the adapter. This capability was introduced in TestStand 2.0.
Additional structure/container/cluster conversion support(and arrays of these) is on the list of potential future TestStand features.
Until new TS features are available, you will have to fetch the itmes one by one.