"Simplify debts" is by far the easiest way to get squared up, say, at the end of the month. However, it confuses the heck out of some of my friends who get confused by the idea of owing a whole bunch of money to one person to whom they might not owe anything directly (eg "Why do I own $100 to person A? She never lent me money" "well it's because you own person B money, and person B owes person A" ... you get the idea.

If you could quickly toggle between the simplified and unsimplified debts, it would enable group members to establish accurate mental models about where the costs are coming from (simplify debts OFF) but then quickly see how that translates to a more streamlined payback system (simplified debts ON). This would be more straightforward than requiring users to dig through the settings to achieve this "toggle".