You can open diagram files (.dnx, .iex, .ifx, and .tpx) from the Diagram
Navigator view.
To open a diagram file, in the Diagram Navigator view,
right-click a diagram file; then click Open.
Tip: When you open a diagram, the diagram editor displays
the diagram. You can select multiple diagram files and open them at the same
time, and use the tabs to switch between open diagrams.