Hook into the PWAL URL filter pwal_url_to_like

gistfile1.php

function theme_pwal_url_filter($href='') {
  // Just replace 'key1' and 'value1' with your custom URL key1=value1 set
  return add_query_arg( array('key1' => 'value1'), $href );
}
add_filter('pwal_url_to_like', 'theme_pwal_url_filter');