I am using Xstore theme which most widely used theme and in best selling in the Theme forest.
I connected with theme support team and they reverted with the below responce
“For information to your plugin’s developers (you may ask them for help):
1/ Our theme field name iset_variation_gallery_images
(to get variation gallery for any product variation we used next line of php code ->get_post_meta( $product->get_id(), 'et_variation_gallery_images', true );
We suggest you to try next snippet to be added in your child-theme/functions.php
add_filter('woo_feed_custom_fields', 'add_etheme_variation_gallery_image_to_feed', 10, 3);
function add_etheme_variation_gallery_image_to_feed($fields, $product, $variation) {
$image_gallery = get_post_meta($variation->get_id(),'et_variation_gallery_images', true);
if ( (bool)$image_gallery ) {
$fields['variation_image_gallery'] = $image_gallery;
}
return $fields;
}
But this code is not working probably your devloper could take help from this response.