JSFiddle - React, Tailwind, and code Playground

HTML

<ol>
    <li>Here's the section heading</li>
    <ol>
        <li>Here's the subsection heading</li>
        <ol>
            <li>Here's the subsection heading</li>
        </ol>  
    </ol>    
</ol>

JavaScript

var html = "<ul><li>Here's the subsection heading</li></ul>";
function subSection(html){
    $('ol').each(function(){
        $(this).children('li:first-child').append(html);
    });
}
subSection(html);