Awesome thanks! Is there any way to adjust the size of the lightbox (or create another shortcode defining a different lightbox) so that it can be square?
This is not possible by default, needs more further customization, you may consider working with a professional, if you are not familiar to WordPress coding.
I’m familiar enough with coding to adjust it I think. Could you point me in the right direction though? Where would I begin to look for the definition of the “lightbox”?