> But when 6 people simultaneously tried to pay their share of the bill, chaos ensued.

Hasn't that been a fact of life ?

If anything, apps made it barely made easier through splitting either the whole bill equally or offer a bit by bit checking interface.

Otherwise on the role of QR codes and online menu, it actually helps a lot for allergies as everyone can check their for each individual item and adjust accordingly.

Of course one can ask the waiters, but many aren't just competent (ask for wallnut allergy, and they'll come back explaining there's no peanuts). And doing the back and forth on which menu has what allergy is also a PITA, with all the other guests just waiting for it to end.

A good waiter by the time it comes to payment will know the dynamic of the group and help them organize quickly.