JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li><a href="#">First</a></li>
    <li><a href="#">Second</a>
        <ul>
            <li><a href="#">Second - 1</a></li>
            <li><a href="#">Second - 2</a></li>
            <li><a href="#">Second - 3</a>
                <ul>
                    <li><a href="#">Aaa</a></li>
                    <li><a href="#">Bbb</a></li>
                    <li><a href="#">Ccc</a></li>
                </ul>
            </li>
        </ul>
    </li>
    <li><a href="#">Third</a></li>
</ul>

JavaScript

$('li > ul').before('<span class="arrow">Span is here</span>');