.se-toolbar-btn-letter-spacing .se-dropdown-trigger-btn {
  position: relative;
  min-width: 50px;
}
.se-toolbar-btn-letter-spacing .se-dropdown-trigger-btn::before {
  content: '';
  position: absolute;
  background-size: 15px 15px;
  width: 15px;
  height: 15px;
  top: 9px;
  left: 8px;
  background-image: url('https://gw.alipayobjects.com/mdn/rms_c791a4/afts/img/A*SaqdTZgR0YYAAAAAAAAAAABkARQnAQ');
}