var czml = [
      {
        "id" : "document",
        "name" : "CZML Geometries: Polygon",
        "version" : "1.0"
      }, {
        "id" : "orangePolygon",
        "name" : "Orange polygon with per-position heights and outline",
        "polygon" : {
          "positions" : {
            "cartographicDegrees" : [
              -70.0, 35.0, 100000,
              -72.0, 37.0, 0,
              -68.0, 35.0, 0
            ]
          },
          "material" : {
            "solidColor" : {
              "color" : {
                "rgba" : [255, 100, 0, 100]
              }
            }
          },
      "extrudedHeight" : 0,
      "perPositionHeight" : true,
      "outline" : true,
      "outlineColor" : {
        "rgba" : [0, 0, 0, 255]
      }
    }
  },


    {
    "id" : "orangePolygon2",
    "name" : "Orange polygon with per-position heights and outline",
    "polygon" : {
      "positions" : {
        "cartographicDegrees" : [
          -70.0, 35.0, 100000,
          -70.0, 33.0, 0,
          -68.0, 35.0, 0
        ]
      },
      "material" : {
        "solidColor" : {
          "color" : {
            "rgba" : [255, 100, 0, 100]
          }
        }
      },
      "extrudedHeight" : 0,
      "perPositionHeight" : true,
      "outline" : true,
      "outlineColor" : {
        "rgba" : [0, 0, 0, 255]
      }
    }
  },

    {
    "id" : "orangePolygon3",
    "name" : "Orange polygon with per-position heights and outline",
    "polygon" : {
      "positions" : {
        "cartographicDegrees" : [
          -70.0, 35.0, 100000,
          -70.0, 33.0, 0,
          -72.0, 37.0, 0,
        ]
      },
      "material" : {
        "solidColor" : {
          "color" : {
            "rgba" : [255, 100, 0, 100]
          }
        }
      },
      "extrudedHeight" : 0,
      "perPositionHeight" : true,
      "outline" : true,
      "outlineColor" : {
        "rgba" : [0, 0, 0, 255]
      }
    }
  }
];

var viewer = new Cesium.Viewer('cesiumContainer');
var dataSource = Cesium.CzmlDataSource.load(czml);
viewer.dataSources.add(dataSource);
viewer.zoomTo(dataSource);

var czml = [
  {
    "id" : "document",
    "name" : "CZML Geometries: Polyline",
    "version" : "1.0"
  },
  {
    "id" : "redLine",
    "name" : "Red line on the surface",
    "polyline" : {
      "show": false,
      "positions" : {
        "cartographicDegrees" : [
          -75, 35, 0,
          -125, 35, 0
        ]
      },
      "material" : {
          "polylineOutline": {
              "color": {"rgba": [255, 0, 0, 255]},
              "outlineColor": {"rgba": [255, 255, 255, 255]},
              "outlineWidth": 2.0
          }
      },
      "width" : 5
    }
  },
  {
    "id" : "purpleLine",
    "name" : "Purple straight line at height",
    "polyline" : {
      "show": false,
      "positions" : {
        "cartographicDegrees" : [
          -125, 35, 0,
          -170, 35, 0
        ]
      },
      "material" : {
          "polylineOutline": {
              "color": {"rgba": [148, 0, 211, 255]},
              "outlineColor": {"rgba": [255, 255, 255, 255]},
              "outlineWidth": 2.0
          }
      },
      "width" : 5
    }
  }
];

var viewer = new Cesium.Viewer('cesiumContainer');
var dataSource = new Cesium.CzmlDataSource();
dataSource.load(czml);
viewer.dataSources.add(dataSource);
viewer.zoomTo(dataSource);

var handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
handler.setInputAction(
    function () { 
        dataSource.entities.getById('purpleLine').polyline.show = true;
        dataSource.entities.getById('redLine').polyline.show = true;

    },
    Cesium.ScreenSpaceEventType.LEFT_CLICK
);

By : https://github.com/AnalyticalGraphicsInc/cesium/issues/3598