function add_order_total_field( $meta_fields ) {

    $meta_fields['order_total'] = array(
        'label' => 'Last Order Total',
        'group' => 'woocommerce',
    );

    return $meta_fields;

}

add_filter( 'wpf_meta_fields', 'add_order_total_field' );

function get_order_total( $order_data, $order ) {

    $order_data['order_total'] = $order->get_total();

    return $order_data;

}

add_filter( 'wpf_woocommerce_customer_data', 'get_order_total', 10, 2 );