Hi there!

Thanks for your query.

A shortcode is not available, as per my knowledge.

However, there is no other way to add SP Easy Image Gallery to a Joomla article than as a module.

I have just made a search and found out a third party extension in JED: https://extensions.joomla.org/extension/wt-sp-easy-image-gallery-insert/

Please note that I did not test this on my own. You can have a look into this if this is what you are looking for. But please keep a full backup of your site before trying anything new so that you can go back to your working state anytime. Regular backup is really so much important:)

Best Regards