ScrollBar

<nav class="scrollbar" style="max-height: 50vh">
    <ul>
        <li><a href="">...</a></li>
        ...
    </ul>
</nav>

.scrollbar {
    scrollbar-width: thin;
    scrollbar-color: rgba(255, 255, 255, 0.50) rgba(255, 255, 255, 0.20);
    overflow-y: auto;
}
.scrollbar::-webkit-scrollbar {
    width: 8px;
}
.scrollbar::-webkit-scrollbar-track {
    background-color: rgba(255, 255, 255, 0.20);
}
.scrollbar::-webkit-scrollbar-thumb {
    background-color: rgba(255, 255, 255, 0.30);
}