Shortcode to add custom fields to the product description https://wpsites.net/?p=114180

functions.php

// Add custom field to product general settings metabox
function custom_product_general_fields() {
    global $woocommerce, $post;

    echo '<div class="options_group">';

    // Custom field
    woocommerce_wp_textarea_input(
        array(
            'id'          => '_custom_product_description',
            'label'       => __('Custom Product Description', 'your-textdomain'),
            'placeholder' => '',
            'desc_tip'    => 'true',
            'description' => __('Enter a custom description for the product.', 'your-textdomain')
        )
    );

    echo '</div>';
}
add_action('woocommerce_product_options_general_product_data', 'custom_product_general_fields');

// Save custom field value
function save_custom_product_general_fields($post_id) {
    $custom_description = isset($_POST['_custom_product_description']) ? $_POST['_custom_product_description'] : '';
    update_post_meta($post_id, '_custom_product_description', sanitize_text_field($custom_description));
}
add_action('woocommerce_process_product_meta', 'save_custom_product_general_fields');


// Define the shortcode function
function custom_product_description_shortcode() {
    global $product;

    // Get the custom field value
    $custom_description = get_post_meta($product->get_id(), '_custom_product_description', true);

    // Output the custom field value
    if (!empty($custom_description)) {
        return '<div class="custom-product-description">' . wpautop($custom_description) . '</div>';
    }

    return ''; // Return empty string if the custom field is not set
}
add_shortcode('custom_product_description', 'custom_product_description_shortcode');