Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Objects
ID_ST_OBJECT_OBJECTSParameter: Hidden
ID_ST_OBJECT_LINE_HIDDENParameter: Visible
ID_ST_OBJECT_LINE_VISIBLEParameter: Type
ID_ST_OBJECT_SPLINE_TYPEParameter: Intermediate Points
ID_ST_OBJECT_SPLINE_INTERPOLATIONParameter: Number
ID_ST_OBJECT_SPLINE_SUBDParameter: Angle
ID_ST_OBJECT_SPLINE_ANGLEParameter: Maximum Length
ID_ST_OBJECT_SPLINE_LENGTHParameter: Mode
ID_ST_OBJECT_LINES_MODEParameter: Lines
ID_ST_OBJECT_LINESParameter: Border
ID_ST_OBJECT_BORDERParameter: Edges
ID_ST_OBJECT_EDGESParameter: Contour UVW
ID_ST_OBJECT_UVW