ui/src/main/java/ucar/util/prefs/ui/PrefPanel.java
public void addEmptyRow(int row, int size) {
    layoutComponents.add( new LayoutComponent( null, size, row, null));
  }
public void addEmptyRow(int row, int size) {
    layoutComponents.add( new LayoutComponent( null, size, row, null));
  }
Add a seperator after the last field added.