Defines the visual appearance of GeometryEditor geometries when this tool is in use. When a GeometryEditorTool is created, a consistent set of default symbology appropriate for that tool type is applied to its property. For example, FreehandTool and ShapeTool define all vertex symbols as null by default because they use drag gestures to define entire parts of polyline and polygon geometries, whereas the VertexTool defines non-null vertex symbols because it is important to be able to see and interact with individual vertices when editing geometries with this tool.