Add Taxonomy by Frontend using JetFormBuilder.php

<?php

/*
Author: Dante Testa
Date: 26/06/2023
www.dantetesta.com.br
*/

add_action( 'jet-form-builder/custom-action/add_tax', function( $request, $action_handler ) {
    if (!isset($request['nome']) || !isset($request['taxonomia'])) {
        return;
    }

    $terms = array_map('sanitize_text_field', explode(',', $request['nome']));
    $taxonomy = sanitize_text_field($request['taxonomia']);

    if (!taxonomy_exists($taxonomy)) {
        return;
    }

    foreach ($terms as $term) {
        // Check if the term already exists
        $existing_term = term_exists($term, $taxonomy);

        // If the term doesn't exist and there was no error, create it
        if ($existing_term === null) {
            $result = wp_insert_term($term, $taxonomy);
            if (is_wp_error($result)) {
                // Handle the error here
            }
        }
    }
}, 10, 2 );