You’ll have to save the diagram position and scale after loading in order to set them back. Of course the view might not look the same or might not be possible if your users have moved objects.
Note that CommandHandler has resetZoom, also. (myDiagram.commandHandler.resetZoom()) The user can type Ctrl-0 to invoke that command.
Remember the values of Diagram.scale and Diagram.position in two variables. When you want to restore those two properties, set Diagram.scale first, because changing the scale is likely to change the Diagram.position.