Menu: View->Mode
This command lets you choose the GiD mode you wish to work with (Preprocess or Postprocess), and the different visualization options in each mode:
Preprocessing: This command allows Mesh or Geometry visualization to be set.
Toolbar: 
The Toggle command changes from one visualization to another. If mesh visualization is selected and no mesh exists, you are asked to generate one.
Postprocessing: This command allows Graphs or Mesh visualization to be set.
This command allows you to move between default mesh visualization and graphs visualization.