We received some follow-up separately, and it sounds like the original use case was to be able to settle up a specific expense separately and still have Simplify debts work for the rest of the group.

In this case, you can always use the Settle up button in the group to record a payment between any group members equal to the amount owed on the specific expense. These payments will then be included in the Simplify debts algorithm and the balances will work out correctly.

If this is not what you were looking for, please send us a note at support@splitwise.com