You should use hook wpo_cart_updated_additional_data.


For example, you installed "WooCommerce Account Funds"  and want to  show amount funded for this customer.


if ( class_exists( 'WC_Account_Funds' ) ) {
  add_filter( 'wpo_cart_updated_additional_data', 
   function ( $additional_data, $cart_data ) {
    if ( !empty( $cart_data['customer']['id'] ) ) {
      $additional_data[] = array(
      'title' => __( 'Amount Funded', 'woocommerce-account-funds' ),
      'value_without_tax' => '',
      'value_total' => WC_Account_Funds::get_account_funds( $cart_data['customer']['id'], true ),
      );
    }
    return $additional_data;
  }, 10, 2 );
}