Please add a token to render the quantity data of the cart.

Because "quantity" is on the order_item level. What you want to do can be done by going through all the order items and summing the 'quantity' field. So it must be a custom token.

Thanks a ton for your response. How do you think it'd be best to achieve what you propose?
This needs to be achieved with the Custom Token module?
https://www.drupal.org/project/token_custom →

This request is out of the scope of this module. The custom tokens can be added to a custom module.