Hello @anthony.viel
Looking through the API docs for MangoPay there is an endpoint to which you could connect - Card Object endpoint which will return an Alias parameter as a string that is a partially obfuscated version of the credit card number.
You can use it in the workflow as something like the result of step and get the alias :truncate from end to and write it to the current user. And on the design side, you just look it up and display it as in the example above.
Though I did not try their API, but should be doable.
Hope it helps. 