Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Layer Value
ID_MT_LAYER_VALUE
Parameter: Mode
ID_MT_LAYER_MODE
Parameter: Mute
ID_MT_LAYER_MUTE
Parameter: Solo
ID_MT_LAYER_SOLO
Parameter: Passthrough
ID_MT_LAYER_PASSTHROUGH
Parameter: Active
ID_MT_LAYER_ACTIVE
Parameter: Quaternion Interpolation
ID_MT_LAYER_QUATERNION