Showing levelized content is a feature of the Graph view. When a Graph view is requested, Sonargraph organizes nodes in a way that given each edge of the graph and both From and To endpoints of the edge, the From endpoint will always be in a greater level than the To endpoint.

Levels in Graph View
Figure 8.33. Levels in Graph View

This way of layouting immediately gives the user an idea about the coupling among the selected elements that form the content of the view and how modifications will impact elements that belong to different levels.