Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Strength
MGSPLINEEFFECTOR_STRENGTH
Parameter: Mode
MGSPLINEEFFECTOR_OFFSETMODE
Parameter: Relative Offset Axis
MGSPLINEEFFECTOR_RELATIVEAXIS
Parameter: Falloff Modifier
MGSPLINEEFFECTOR_FALLOFFSTRENGTH
Parameter: Spline
MGSPLINEEFFECTOR_SPLINE
Parameter: Up Vector
MGSPLINEEFFECTOR_UP_VECTOR
Parameter: Rail
MGSPLINEEFFECTOR_RAIL_SPLINE
Parameter: Target Rail
MGSPLINEEFFECTOR_TARGET_RAIL
Parameter: Offset
MGSPLINEEFFECTOR_OFFSET
Parameter: Start
MGSPLINEEFFECTOR_START
Parameter: End
MGSPLINEEFFECTOR_END
Parameter: Clamp
MGSPLINEEFFECTOR_CLAMP
Parameter: Segment Mode
MGSPLINEEFFECTOR_SEGMENTMODE
Parameter: Segment
MGSPLINEEFFECTOR_SEGMENTINDEX
Parameter: Seed
MGSPLINEEFFECTOR_SEGMENTSEED
Parameter: Transform Mode
MGSPLINEEFFECTOR_TRANSFORMMODE
Parameter: Position
MGSPLINEEFFECTOR_POSITION_ACTIVE
Parameter: Rotation
MGSPLINEEFFECTOR_ROTATION_ACTIVE
Parameter: R
MGSPLINEEFFECTOR_ROTATION