A way to modify the values of data that will be send in Webhook, in this specific case the submission ID field is not sending the Entry ID, it's sending a default text

forminator_webhook_submission_id_fix.php

<?php
/**
 * Plugin Name: [Forminator Pro] - Replace Submission ID before send Webook request
 * Plugin URI: https://wpmudev.com/
 * Description: Replace Submission ID before send Webook request
 * Author: Alfredo Galano Loyola @ WPMUDEV
 * Author URI: https://wpmudev.com/
 * License: GPLv2 or later
 */
if (!defined('ABSPATH')) {
    exit;
}
// No need to do anything if the request is via WP-CLI.
if (defined('WP_CLI') && WP_CLI) {
    return;
}

if (!class_exists('WPMUDEV_Forminator_SubmissionID_Webhook_Fix')) {

    class WPMUDEV_Forminator_SubmissionID_Webhook_Fix
    {
        /**
         * $forms used to define the form and the hidden field that will be used. 
         * It's possible use the feature in several forms using the format
         * formID =>Hidden_Field_Name 
         * The Hidden Field is the one set to use the Submission ID value
         */
        private $forms = array(
            "1049461" => 'hidden-1'
        );
        
        private $form_fields;


        private static $_instance = null;

        public static function get_instance()
        {

            if (is_null(self::$_instance)) {
                self::$_instance = new WPMUDEV_Forminator_SubmissionID_Webhook_Fix();
            }

            return self::$_instance;
        }

        private function __construct()
        {
            $this->init();
        }

        public function init()
        {
            // Do some checks here
            if (!defined('FORMINATOR_VERSION') || FORMINATOR_VERSION < '1.12' || !class_exists('Forminator_API')) {
                return;
            }

           add_filter('forminator_addon_webhook_api_request_data', array($this, 'replace_webhook_arg_data'), 1, 3);

        }

        public function replace_webhook_arg_data($args, $verb, $path){
            if(isset($this->forms[$_REQUEST["form_id"]])){
                $this->form_fields = $this->forms[$_REQUEST["form_id"]];
                if(isset($args[$this->form_fields]) && $args[$this->form_fields]==="submission_id")
                $entry = Forminator_Form_Entry_Model::get_latest_entry_by_form_id( $_REQUEST["form_id"]);

                $args[$this->form_fields]=$entry->entry_id;
            }
            return $args;
            
        }

    }

    add_action('plugins_loaded', function () {
        return WPMUDEV_Forminator_SubmissionID_Webhook_Fix::get_instance();
    });
}

var_dump($arg) looks like this:
array(16) { ["name-1"]=> string(9) "Alfredito" ["hidden-1"]=> string(13) "submission_id" ["hidden-2"]=> string(7) "1049461" ["referer_url"]=> string(0) "" ["_wp_http_referer"]=> string(26) "/submission-id-to-zappier/" ["page_id"]=> string(7) "1049462" ["form_type"]=> string(7) "default" ["current_url"]=> string(54) "https://myblank.tempurl.host/submission-id-to-zappier/" ["render_id"]=> string(1) "0" ["forminator_current_location"]=> string(22) "11.9668736 -86.1011968" ["forminator_current_address"]=> string(0) "" ["forminator_current_location_error"]=> string(0) "" ["_forminator_user_ip"]=> NULL ["geolocation"]=> NULL ["form-title"]=> string(24) "Submission ID To Zappier" ["entry-time"]=> string(19) "2024-04-30 10:28:51" }