JSFiddle - React, Tailwind, and code Playground

HTML

<div id="bar">
    <ul>
        <li>Odkaz</li>
        <li>Odkaz</li>
        <li>Odkaz</li>
    </ul>
</div>

CSS

#bar {
    width: 200px;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    background-color: Grey;
    overflow-y: auto; /* ZDE */
}

ul {
    list-style-type: none;
}

li { height: 300px; }