Custom !!denied_reason!! for Approvals Denied Email Templates.

my-pmpro-approvals-denied-message.php

<?php
/**
 * Add a custom field !!denied_reason!! to be used in Approvals Denied Email.
 * Add this code to your site by following this guide - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_denied_message( $data, $member ) {
    $denied_reason = get_user_meta( $member->ID, 'my_field_key', true ); // Change 'my_field_key' to the meta key of your custom field.
    $data['denied_reason'] = $denied_reason;
    return $data;
}
add_filter( 'pmpro_approvals_member_denied_email_data', 'my_pmpro_denied_message', 10, 2 );