Hi,
As you can see on the demo page title, that is an example to combine the plugin with the Elementor WooCommerce products widget. That widget is part of the Elementor Pro plugin package (that is doing the output the plugin just does the filtering). That is a feature we had been working on for quite some time now, and it was rolled out about a week ago.
You can find the related documentations for them here:
– Elementor integration
– Elementor Posts Widget filter
– Elementor Products Widget filter