TWINT, the Cumulus card can NOT be stored as a customer card (similar to the Coop Supercard)! It is only possible to store the TWINT payment mode in the Migros app under "Pay with the app", just as you can store the Migros bank account, Mastercard, Visa, PostFinance and American Express cards, as well as Migros gift cards... But I suspect this is not the procedure you are looking for.... are indeed two pairs of shoes ;-)
Thanks for your answer, but it's not really the solution paragraph. A more customer-friendly method would be to deposit the card in the same way as Coop.