Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Reduce Children Combined
POLYREDUXOBJECT_REDUCE_ALL_AS_ONEParameter: Reduction Strength
POLYREDUXOBJECT_STRENGTHParameter: Triangle Count
POLYREDUXOBJECT_TRIANGLE_COUNTParameter: Vertex Count
POLYREDUXOBJECT_VERTEX_COUNTParameter: Remaining Edges
POLYREDUXOBJECT_REMAINING_EDGES_COUNTParameter: Preserve 3D Boundaries
POLYREDUXOBJECT_PRESERVE_3D_BOUNDARYParameter: Preserve UV Boundaries
POLYREDUXOBJECT_PRESERVE_UV_BOUNDARYParameter: Boundary Reduction Angle
POLYREDUXOBJECT_REDUCE_BOUNDARY_ANGLE