shortdark

Adds an accordion using plaing javascript and CSS, not jQuery.
Please let me know if you like this plugin by leaving a review or <a href="http://www.shortdark.net/contact-me/" rel="nofollow ugc">contacting me</a>.
Go to the <a href="http://www.shortdark.net/wordpress-plugin/" rel="nofollow ugc">Shortdark WordPress plugin page</a> for more information.

Javascript CSS Accordion

Adds an accordion using plain javascript and CSS, not jQuery. Tested on PHP 5 through PHP 8.

sevenspark

Bellows is an awesome accordion menu for WordPress. It works with the WordPress menu system to allow you to build beautiful accordion menus for your site.
<a href="https://wpaccordionmenu.com/free/" rel="nofollow ugc">Bellows Lite Demo</a> 
<a href="https://wpaccordionmenu.com/" rel="nofollow ugc">Bellows Full Demo</a>
Get started: <a href="http://sevenspark.com/docs/bellows/quick-start/lite" rel="nofollow ugc">Bellows Quick Start Guide</a>
<h4>Feature Overview</h4>
<ul>
<li>Fully functional accordion menu</li>
<li>Multiple submenu levels</li>
<li>3 included skin presets</li>
<li>Multi- or single-folding</li>
<li>Expand current submenu automatically option</li>
<li>Shortcode integration – add an accodion menu to yoru site anywhere you can add shortcodes</li>
<li>Widget integration – add an accordion menu to your widgetized theme areas</li>
</ul>

Bellows Accordion Menu

A flexible and robust accordion menu plugin

Javascript CSS Accordion vs Bellows Accordion Menu