.dropdown-submenu {
    position: relative;
}

.dropdown-submenu a::after {
    transform: rotate(-90deg);
    position: absolute;
    right: 6px;
    top: 0.6em;
}

.dropdown-submenu .dropdown-menu {
    top: 0;
    left: 100%;
    /*margin-left: .1rem;*/
    margin-right: .1rem;
    margin-top: -1.5rem;
}