Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Offset
MDATA_SMOOTHSHIFT_OFFSETParameter: Offset Variation
MDATA_SMOOTHSHIFT_VARIANCEParameter: Subdivision
MDATA_SMOOTHSHIFT_SUBDIVISIONParameter: Create N-gons
MDATA_SMOOTHSHIFT_CREATENGONSParameter: Preserve Groups
MDATA_SMOOTHSHIFT_PRESERVEGROUPSParameter: Maximum Angle
MDATA_SMOOTHSHIFT_ANGLE