Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Offset
MDATA_SMOOTHSHIFT_OFFSET
Parameter: Offset Variation
MDATA_SMOOTHSHIFT_VARIANCE
Parameter: Subdivision
MDATA_SMOOTHSHIFT_SUBDIVISION
Parameter: Create N-gons
MDATA_SMOOTHSHIFT_CREATENGONS
Parameter: Preserve Groups
MDATA_SMOOTHSHIFT_PRESERVEGROUPS
Parameter: Maximum Angle
MDATA_SMOOTHSHIFT_ANGLE