The simpliest code is

<div data-role="collapsible-set"> <div data-role="collapsible" data-collapsed="false"> <h3>Section 1</h3> <p>I'm the collapsible set content for section 1.</p> </div> <div data-role="collapsible"> <h3>Section 2</h3> <p>I'm the collapsible set content for section 2.</p> </div> </div>

What would I need to add to have a nested collapsible set....for example, in Section 2 - so I can have an section 2.1, 2.2, 2.3 (and my <p> text under those sections), but they all remain under the main section 2.

Thank you in advance.