JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" name="" onclick="Toggle('Knickers')" /> Knickers
    <div id="Knickers" style="padding:2px; background-color:#ffc; display:none;">
        <input type="checkbox" name="" onclick="Toggle('Simon')" /> Simon<br>
        <div id="Simon" style="padding:2px; background-color:#ffc; display:none;">
            <input type="checkbox" name=""/> Stripy Top
            <input type="checkbox" name=""/> Naughiness</div>
        <input type="checkbox" name="" onclick="Toggle('Dan')" /> Dan<br>
        <div id="Dan" style="padding:2px; background-color:#ffc; display:none;">
            <input type="checkbox" name=""/> Stripy Top
            <input type="checkbox" name=""/> Naughiness</div>
        <input type="checkbox" name="" onclick="Toggle('Emma')" /> Emma<br>
        <div id="Emma" style="padding:2px; background-color:#ffc; display:none;">
            <input type="checkbox" name=""/> Stripy Top
            <input type="checkbox" name=""/> Naughiness</div>
    </div><br>
<input type="checkbox" name="" onclick="Toggle('Long Parliament')" /> The Long Parliament
    <div id="Long Parliament" style="padding:2px; background-color:#ffc; display:none;">
        <input type="checkbox" name="" onclick="Toggle('Darren')" /> Darren<br>
        <div id="Darren" style="padding:2px; background-color:#ffc; display:none;">
            <input type="checkbox" name=""/> Stripy Top
            <input type="checkbox" name=""/> Naughiness</div>
        <input type="checkbox" name="" onclick="Toggle('Emma')" /> Emma<br>
        <div id="Emma" style="padding:2px; background-color:#ffc; display:none;">
            <input type="checkbox" name=""/> Stripy Top
            <input type="checkbox" name=""/> Naughiness</div>
    </div><br>
<input type="checkbox" name="" onclick="Toggle('Hot Booth')" /> Hot Booth
    <div id="Hot Booth" style="padding:2px; background-color:#ffc; display:none;">
        <input type="checkbox" name="" onclick="Toggle('Dan')" /> Dan<br>
        <div...

JavaScript

function Toggle(id) {
            if (document.getElementById(id).style.display == "none" || document.getElementById(id).style.display == "") {
                document.getElementById(id).style.display = "block";
            } else if (document.getElementById(id).style.display == "block") {
                document.getElementById(id).style.display = "none";
            } else {
                document.getElementById(id).style.display = "none";
            }
        }