Example

$form->addHeading('Section 1');
$form->startFieldset();
$form->addHtml('<p class="text-muted pt-2 pb-5">// Section 1 content here ...</p>');
$form->endFieldset();

$form->addHeading('Section 2');
$form->startFieldset();
$form->addHtml('<p class="text-muted pt-2 pb-5">// Section 2 content here ...</p>');
$form->endFieldset();

$form->addHeading('Section 3');
$form->startFieldset();
$form->addHtml('<p class="text-muted pt-2 pb-5">// Section 3 content here ...</p>');
$form->endFieldset();

Section 1

// Section 1 content here ...

Section 2

// Section 2 content here ...

Section 3

// Section 3 content here ...

<h4>
    <span class="js-badger-accordion-header">Section 1</span>
</h4>
<fieldset class="badger-accordion__panel js-badger-accordion-panel -ba-is-hidden">
    <div class="js-badger-accordion-panel-inner">
        <p class="text-muted pt-2 pb-5">// Section 1 content here ...</p>
    </div>
</fieldset>
<h4>
    <span class="js-badger-accordion-header">Section 2</span>
</h4>
<fieldset class="badger-accordion__panel js-badger-accordion-panel -ba-is-hidden">
    <div class="js-badger-accordion-panel-inner">
        <p class="text-muted pt-2 pb-5">// Section 2 content here ...</p>
    </div>
</fieldset>
<h4>
    <span class="js-badger-accordion-header">Section 3</span>
</h4>
<fieldset class="badger-accordion__panel js-badger-accordion-panel -ba-is-hidden">
    <div class="js-badger-accordion-panel-inner">
        <p class="text-muted pt-2 pb-5">// Section 3 content here ...</p>
    </div>
</fieldset>