JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <td>
            <span class="arrow"></span>
            Some content
        </td>
        <td>Some content</td>
    </tr>
</table>

CSS

table {
    margin:100px;
}

td {
    position: relative;
}

span.arrow {
    display:none;
    width:20px;
    height:20px;
    position: absolute;
    left:    -20px;
    border:1px solid red;
}

tr:hover span.arrow {
    display:block;
}