Filter to add conversion link - By WebToffee (Product Feed for WooCommerce By WebToffee)

functions.php

<?php //Do not add this line of code
add_filter('wt_feed_filter_product_link','wt_feed_filter_product_link_utm', 10, 2);
function wt_feed_filter_product_link_utm($link, $product){
      return $link.'?utm_source=summer-sale&utm_medium=feed&utm_campaign=summer-sale';
                    
 }