Add custom lightbox attribute to menu item optin monster.

functions.php

/* Add custom lightbox attribute to the menu Optin Monster
*/ 
function prefix_menu_item_extra_atts( $atts, $item, $args )
{
	if ( $item->object_id == '652') {
		 $atts['data-optin-slug'] = 'uc20zebirdm018gi';
		 $atts['class'] = 'manual-optin-trigger';
	}
   
    return $atts;
}
add_filter( 'nav_menu_link_attributes', 'prefix_menu_item_extra_atts', 10, 3 );