Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Selection
MDATA_MEASURE_SELECTIONParameter: Show
MDATA_MEASURE_VISIBLEParameter: New Measure
MDATA_MEASURE_NEWParameter: Delete Measure
MDATA_MEASURE_DELETEParameter: Create Object
MDATA_MEASURE_CREATEOBJECTParameter: 3rd Point
MDATA_MEASURE_3RD_POINTParameter: Measure Distance 1
MDATA_MEASURE_SHOWDIST1Parameter: Distance 1
MDATA_MEASURE_DIST1Parameter: Revert Direction
MDATA_MEASURE_DIR1Parameter: Measure Distance 2
MDATA_MEASURE_SHOWDIST2Parameter: Distance 2
MDATA_MEASURE_DIST2Parameter: Revert Direction
MDATA_MEASURE_DIR2Parameter: Measure Angle
MDATA_MEASURE_SHOWANGLEParameter: Angle
MDATA_MEASURE_ANGLEParameter: Revert Axis
MDATA_MEASURE_FIXROTParameter: Point Color
MDATA_MEASURE_COLORPParameter: Color 1
MDATA_MEASURE_COLOR1Parameter: Color 2
MDATA_MEASURE_COLOR2Parameter: Point 1 Object
MDATA_MEASURE_PNT1_LINKParameter: Point 1 Mode
MDATA_MEASURE_PNT1_MODEParameter: Point 1 Index
MDATA_MEASURE_PNT1_IDXParameter: Point 1 Position
MDATA_MEASURE_PNT1_VECTORParameter: Point 2 Object
MDATA_MEASURE_PNT2_LINKParameter: Point 2 Mode
MDATA_MEASURE_PNT2_MODEParameter: Point 2 Index
MDATA_MEASURE_PNT2_IDXParameter: Point 2 Position
MDATA_MEASURE_PNT2_VECTORParameter: Point 3 Object
MDATA_MEASURE_PNT3_LINKParameter: Point 3 Mode
MDATA_MEASURE_PNT3_MODEParameter: Point 3 Index
MDATA_MEASURE_PNT3_IDXParameter: Point 3 Position
MDATA_MEASURE_PNT3_VECTOR