struct in UnityEditor.Experimental.UIElements.GraphView
Switch to Manual此结构表示用户开始创建图形节点时的上下文。
| index | The index where the created node will be inserted. |
| screenMousePosition | 在屏幕的坐标空间中发起创建节点请求的单击位置。 |
| target | The VisualElement where the created node will be added. |