show_custom_column_to_woocommerce_orders.php

<?php

add_action( 'manage_shop_order_posts_custom_column', 'musilda_show_weight_in_order_column' );

function musilda_show_weight_in_order_column( $column ) {
        global $post;

        if ( empty( $post->ID ) ) {
                return;
        }

        if ( $column == 'order-weight' ) {
                $weigth = get_post_meta( $post->ID, 'order-weight', true );
                echo !empty( $weigth ) ? $weigth : '';
        }
}