static int withLeftMargin_defaultWidth = 6;

static JPanel withLeftMargin(Component c) {
  ret withLeftMargin(withLeftMargin_defaultWidth, c);
}

static JPanel withLeftMargin(final int margin, final Component c) {
  ret swing(func -> JPanel {
    JPanel p = new JPanel(new BorderLayout);
    p.setBorder(BorderFactory.createEmptyBorder(0, margin, 0, 0));
    p.add(c);
    ret p;
  });
}

Began life as a copy of #1006306