Diego Bunq doesn't have a savings account in the traditonal sense. All accounts can be used for anything.
If you created a Savings Goal account it will show up differently in the app. You can set a target and it will show the percentage you've reached, it won't show the normal payment icons and so on.
But you can use the account for payments, direct debits just like any other. It takes some more steps to select the Savings Goal account to be used for payment but it's not impossible.