Add privacy options for payments. for eg: if a group contains A, B & C. a split is added between A&B then C shouldnt be able to see it.
this checkbox option can be made optional while adding the bill, the payer can check the checkbox if he feels 'not involved' users need not see the split. this will save unnecessary temporary duplicate groups.

Unfortunately, we don’t have plans to support custom privacy settings like this on an expense-by-expense basis, as we think it makes it too complicated to understand who has access to what.
If you’d like to add a single expense that is only visible to the people participating directly in the expense, then you should try adding a “non-group” expense, which does not belong to any particular group. These expenses are only visible to the people involved. Non-group expenses are intended as a way to add expenses and payments with lots of random people, without needing to create a new group every time.