Click the Overview tab as shown in the Diagram view to display a thumbnail image of the current diagram:
Using the shaded rectangle that appears in the Overview pane, you can quickly scroll around the diagram. This feature is useful for navigating large diagrams. To close the Overview pane, click anywhere within the Diagram view.
To increase or decrease the size of the Overview pane, position the mouse cursor at the top left hand corner of the pane. The mouse icon changes to a double-headed arrow. Drag the top left corner of the pane to resize it.
