Masonry Gallery Caption change in gallery

Hi,
Try adding the custom class replace-title-with-caption to your masonry gallery element:

then add this code to the end of your child theme functions.php file in Appearance ▸ Editor:

function replace_masonry_gallery_lightbox_title_with_gallery_caption() { ?>
  <script>
window.addEventListener('DOMContentLoaded', function() {
(function($){
$(window).load(function(){  
    $('.av-masonry-gallery.replace-title-with-caption a.av-masonry-entry.lightbox-added').magnificPopup({
    type: 'image',
		image: {
        titleSrc: false,
        markup: '<div class="mfp-figure">'+
                  '<div class="mfp-close"></div>'+
                  '<div class="mfp-top-bar"></div>'+
                  '<div class="mfp-img"></div>'+
                  '<div class="mfp-bottom-bar">'+
                    '<div class="mfp-title"></div>'+
                    '<div class="mfp-counter"></div>'+
                  '</div>'+
                '</div>',
    },
    mainClass:          'avia-popup mfp-zoom-in mfp-image-loaded',
    closeOnContentClick:  false,
    midClick:         true,

    gallery: {
      enabled:      true
    },

    callbacks: {
		markupParse: function (template, values, item) {
			values.title = item.el.closest('.av-masonry-entry').find('.av-masonry-entry-content').text();
		},
        change: function() {
            $(this.content)
                .find('.mfp-top-bar')
                .html(
                    '<h2>' +
                        $(this.currItem.el).attr('title') +
                    '</h2>'
                );
        },
    },
  }); 
  $(document).on('click', '.popup-modal-dismiss', function (e) { 
    $.magnificPopup.close();
  });
});
})(jQuery);
});
</script>
  <?php
}
add_action('wp_footer', 'replace_masonry_gallery_lightbox_title_with_gallery_caption');

The expected result:

This code is based on some shared by Guenni007, thanks Guenni007.

Best regards,
Mike