I got it…
jQuery(document).ready(function() {
jQuery('.ngg-gallery-thumbnail a').each(function() {
jQuery(this).addClass('highslide');
});
jQuery('.ngg-gallery-thumbnail-box').each(function() {
jQuery(this).addClass('post');
});
jQuery(".post").each(function(index) {
jQuery(this).find("a.highslide").each(function() {
this.onclick = function() {
return hs.expand(this);
}
});
});
});
By the way, this solution integrates the Highslide JS with the NextGEN Gallery (https://br.www.ads-software.com/plugins/nextgen-gallery/) under this AjaxLoader plugin…