Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Reference
GV_HIERARCHY_OBJECT_ID
Parameter: Reference Mode
GV_HIERARCHY_PATH_TYPE
Parameter: Start Position
GV_HIERARCHY_START_TYPE_ID
Parameter: Start Distance
GV_HIERARCHY_DISTANCE_ID
Parameter: Reference Path
GV_HIERARCHY_PATH_ID
Parameter: Start Path
GV_HIERARCHY_START_ID
Parameter: Iteration Path
GV_HIERARCHY_ITERATION_ID
Parameter: Exclude
GV_HIERARCHY_EXCLUDE_ID
Parameter: Maximum Iterations
GV_HIERARCHY_INPUT_MAX
Parameter: On
GV_HIERARCHY_OPERATOR_ON
Parameter: Count
GV_HIERARCHY_OUTPUT_COUNT