By default, the "Description" field in the "Media Box" particle does not render shortcodes (for example the Regular Labs Slider).
Anyway, I modified the particle so it now renders shortcodes.
Here's what you need to do:
1. Download the attached media-box-custom.zip
2. UNZIP it on your computer. You will find one file - media-box.html.twig
3. Copy the media-box.html.twig
file to root/templates/TEMPLATE_DIR/custom/particles
(if the particles
folder does not exist, you will need to create it manually). Basically, this step is the same as the one described in the Overriding Particle Source Files
section in the Gantry 5 Documentation.
4. Clear Joomla cache.