GeneratePress Navigation Effect – Triangle indicator

.main-navigation .main-nav ul li[class*="current-menu-"] > a:after{
    position: absolute;
    bottom: calc(50% - 1.5em);
    height: 0;
    width: 0;
    left: -webkit-calc(50% - 8px);
    left: calc(50% - 10px);
    border: 9px solid rgba(0,0,0,0);
    border-bottom-color: currentcolor;
    content: "";
}