Example usage of a Ninja Forms Zapier add-on filter hook for field data sent to Zapier. This can be installed as a plugin using the Download ZIP feature of this Gist interface and the Upload ZIP method in WP. This requires a precise version of the Zapier add-on. Contact Ninja Forms support if you are not sure to have the correct version.

nf-custom-zapier.php

<?php
/*
Plugin Name: Ninja Forms Custom Zapier Data
Description: Testing Ninja Forms hook
Version: 1.0.0
*/

/**
 * Filter a value recorded for Zapier data. To be used with Ninja Forms Zapier >= 3.1.0
 *
 * THIS EXAMPLE is using "listselect_1713786441727" as the field key which value we want to filter. That needs to be adapted to the key of the precise field used in a form.
 * 
 * @param string Value of the field. Can change depending on field type but it was already formatted for Zapier's usage.
 * @param array field data
 */
add_filter('nf_zapier_filter_field_value', function ($value, $field) {

    if ($field['key'] === "listselect_1713786441727") {
        $value = "/gs_paises(fhyjtyjtjtyjytj-tyjtyjjty0000-08888)";
    }

    return $value;
}, 10, 2);