[Plugin: WP UI – Tabs, Accordions, Sliders] Thumbnail – First Image in post should display

If I have this in the template:

<div class="wpui-post-thumbnail">{$thumbnail}</div>
<div class="wpui-post-content">{$excerpt}</div>
<p class="wpui-readmore"><a class="ui-button ui-widget ui-corner-all" href="{$url}" title="Read more from {$title}">Read More...</a></p>

I would have expected it to display the first image in the post, then the excerpt. But it does not display any image. I believe that the plugin only displays the thumbnail if it is set in the Featured Image of the post.

Would it be possible to also have an option to display the first image inserted in the post?

Thanks

https://www.ads-software.com/extend/plugins/wp-ui/