Open a supplement object. For more information on how to do so, see section 8.3.2. In order for you to remove a polygon from the map, the supplement object you are working with must be of a type that allows it to have a shape.
Go to the object card (see image below).
Click the tab called "General" (see image below).
Go to the map (see image below).
Click "Delete Polygon" (see the first image below). When you do so, a dialog asking the following question will open: "Are you sure you want to remove this area?" (see the second image below).
Click "Delete" in the dialog (see the first image below). When you do so, the polygon linked to the supplement object you are working with will be removed from the map (see the second image below).
