Works fine and simple, many too much simple

Hi @iziaweb

We have verified the possibilities of introducing the Cart Weight feature in the back-office. Our developers prepared a code you can implement in your functions.php file.

add_action( 'woocommerce_admin_order_totals_after_total', function ( $order_id ) {
    $order_weight = 0.0;
    try {
        $order = wc_get_order( $order_id );
        foreach ( $order->get_items() as $item ) {
            try {
                $product      = $item->get_product();
                $order_weight += $product->get_weight() * $item->get_quantity();
            } catch (Exception $e) {
                // do nothing.
            }
        }
    } catch (Exception $e) {
        // do nothing.
    }

    if ( $order_weight === 0.0 ) {
        return;
    }
    ?>
        <tr>
            <td colspan="3"><hr/></td>
        </tr>
        <tr>
            <td class="label"><?php esc_html_e( 'Weight', 'woocommerce' ); ?>:</td>
            <td width="1%"></td>
            <td class="total">
                <span class="amount">
                    <?php echo wc_format_weight( $order_weight ); ?>
                </span>
            </td>
        </tr>
    <?php
} );

Please use this article for reference: https://octolize.com/blog/add-custom-code-woocommerce-and-wordpress/.

If you have additional questions, please open a new support thread or contact us at https://octolize.com/support/

Thank you for the review!