Selecting this command opens a new Graph tab in the Sonnet session window, which displays a Cartesian Plot for the project(s) presently displayed.
If you are presently viewing a Cartesian plot, then the new Cartesian Plot will be a duplicate of your present Cartesian Plot. If you are presently viewing a Smith Chart, then the new Cartesian plot will contain S-Parameter curves of the same projects plotted in the Smith Chart.