You can also try selecting, copying, and deleting parts in myDiagram and then click on "Draw Visual Tree" again to see how the visual tree in myDiagram changes.
See also the Visual Tree sample, to show the same visual tree using nodes and links in a traditional tree structure.
This predefined layout is used for placing Nodes in a grid-like arrangement. Nodes can be ordered, spaced apart, and wrapped as needed. This Layout ignores any Links connecting the nodes being laid out. More information can be found in the GoJS Intro.
This predefined layout is used for placing Nodes of a tree-structured graph in layers (rows or columns). For discussion and examples of the most commonly used properties of the TreeLayout, see the Trees page in the Introduction. More information can be found in the GoJS Intro.
The Group class is used to treat a collection of Nodes and Links as if they were a single Node. Those nodes and links are members of the group; together they constitute a subgraph.
A subgraph is not another Diagram, so there is no separate HTML Div element for the subgraph of a group. All of the Parts that are members of a Group belong to the same Diagram as the Group. There can be links between member nodes and nodes outside of the group as well as links between the group itself and other nodes. There can even be links between member nodes and the containing group itself.
More information can be found in the GoJS Intro.