You could use a white line style as mentioned. However this can cause issues in other views. EXAMPLE: I created a window family with a RECTANGULAR pitch adjustable sill. I then placed a triangle (concrete back end fill) between the rectangular sill and the wall. Using the white line style hid this in plan, however when I went to the section view the triangle required a outline but was just showing the hatch pattern. I could probably draw a line to close up the triangle. I think a better idea would be able to select an individual line in a given view and either change its line style or set to <invisible> as the wish. A good example of this can be seen in an Inventor drawing where you can override an individual line to hide it, removing it from the view.