You can reduce an area of a zone or divide a zone into two or more zones using the Subtract from Zone tool in the Image toolbar.
Click the Subtract from Zone button
in the Image toolbar.
The mouse pointer in the image view becomes a drawing tool with a minus sign.
Position the drawing tool at the point where you want to start subtracting from the zone.
Hold down the mouse button and drag the drawing tool in the direction that you want to subtract from the zone.
Release the mouse button when you are finished subtracting from the zone.
The zone border changes to display the modified zone area.
Click the Subtract from Zone button
in the Image toolbar.
The mouse pointer in the image viewer becomes a drawing tool with a minus sign.
Hold the mouse button down and drag the drawing tool over the area where you want to divide the zone.
Release the mouse button when you are done.
The zone border changes to display the modified zone area.