Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Display
ID_MG_TRANSFORM_DISPLAYMODEParameter: P
ID_MG_TRANSFORM_POSITIONParameter: R
ID_MG_TRANSFORM_ROTATEParameter: S
ID_MG_TRANSFORM_SCALEParameter: Color
ID_MG_TRANSFORM_COLORParameter: Weight
ID_MG_TRANSFORM_WEIGHTParameter: Time
ID_MG_TRANSFORM_TIME