B2 Spice A/D v4's graphing powers go beyond simple signal customization and settings. You can create new graphs and pull in signals from other simulations, both digital and analog.

To do so, just create a new blank graph

Go to the Workspace and navigate to the specific circuit's simulation signal that you wish to add to the new blank graph...

and either right-click on it and selecting "add plot to front graph" or simply dragging it over to the new graph.

and continue adding all the signal plots that you want, including digital signals.

Notice that graphs can have different scales. Workshop will automatically adjust the ranges so that all the plots will be shown. However, to get a clearer scale, you can opt to show each plot in its own graph with its own scale.