Hi there,
try this CSS:
@media (min-width: 769px) {
.main-navigation .menu > .menu-item > a::after {
content: "";
position: absolute;
right: 12px;
left: 12px;
bottom: 0;
display: block;
height: 5px;
background-color: #d5db12;
opacity: 0;
transition: opacity 0.2s;
}
.main-navigation .menu > .menu-item.current-menu-item > a::after,
.main-navigation .menu > .menu-item.current-menu-ancestor > a::after,
.main-navigation .menu > .menu-item > a:hover::after {
opacity: 1;
}
}