static int withRightMargin_defaultWidth = 6;

static JPanel withRightMargin(Component c) {
  ret withRightMargin(withRightMargin_defaultWidth, c);
}

static JPanel withRightMargin(final int w, final Component c) {
  ret swing(func -> JPanel {
    JPanel p = marginPanel();
    p.setBorder(BorderFactory.createEmptyBorder(0, 0, 0, w));
    p.add(c);
    ret p;
  });
}

Began life as a copy of #1004959