This command enables or disables horizontal mirroring in the spline window. Mirroring shows you what the opposite wall of the pot will look like at all times. This is useful because it provides immediate visual feedback during spline dragging, unlike the view which normally only updates when spline dragging is complete. You can configure PotterDraw to continuously update the view during spline dragging, by setting the Show Spline Drag in View option to true, but note that doing so may degrade performance.