.dropdown-submenu > .dropdown-menu {
  top: 0;
  left: 100%;
  margin-top: -0.125rem;
}

.dropdown-submenu:hover > .dropdown-menu {
  display: block;
}

.dropdown-submenu > a::after {
  content: '▶';
  float: right;
  margin-left: 0.5em;
  font-size: 0.7em;
}