Wouter🇳🇱 You could try with your phone under your sweater (just kidding).
I have a few accounts with little balance on it at the top of my list and have excluded all but the top account from the "total".
I would not mind if bunq made a "change card/account" widget just like they have for the tap&pay that would only let you change the accounts (pin?) of a card on the fly while queing in the line before the checkout.