Collapsing the outline is not the only way to reduce the number of boxes visible on the diagram. As with Gantt Chart and Calendar views, you can apply a filter to a Network Diagram. Select Project, Filtered For from the menu and select a filter from the cascading list, or use the filter drop-down list on the Formatting toolbar.
Figure 8.10 shows the Critical filter applied to the project. Note that Tasks 11 through 17 are not displayed; they are noncritical tasks and would appear as blue boxes if all tasks were visible.