.dropdown-submenu {
              position: relative;
          }
          .dropdown-submenu .dropdown-menu {
              top: 0;
              left: 100%;
              margin-top: -1px;
          }
          .dropdown-submenu a::after {
            transform: rotate(-90deg);
            position: absolute;
            right: 6px;
            top: .8em;
          }

          .dropdown-submenu .dropdown-menu {
            top: 0;
            left: 100%;
            margin-left: .1rem;
            margin-right: .1rem;
          }