You can change the view using the Distort menu as you create your effect.

The Distort module makes it easy to toggle between Input1 and Input2 clips or mattes independently in each viewport. For example, you can display Input1 in one viewport, and the matte of Input2 in another viewport.

Within a particular view, you can also toggle on or off clips to facilitate your work or create different effects. For example, if you loaded two inputs and their mattes, as well as a background clip, you can turn on or off any of the five clips that together make up the composite.