How can I see all classes of my project in diagram at the same time?

I can only see classes from the specific folders, or the ones that I will manually add to a diagram, but is there a way to show in UML Diagram all classes from the whole project? Or from subfolders of specific folder? My projects are generally very granular and I'm using many folders... I found this: http://stackoverflow.com/questions/8942751/use-intellij-to-generate-class-diagram but I cannot find an option for expanding nodes.

Regards!