Recently, we received many users' requests to add the options to make advance/cash/partial payments to offset balances. You can actually do this with the current version of the app. Here are some scenarios:
Let's say we have 3 people A, B, C in the group.
1. A makes an advance payment of $100 before the trip:
a) Create a new receipt with $100;
b) Add a new category called "Advance Payment" or whatever you like;
c) Choose A as the payer and share "evenly";
d) Save the receipt.
2. During the trip, one day B wants to clear his debits ($30) with C:
a) Create a new receipt with $30;
b) Add a new category called "Cash Payment" or whatever you like;
c) Choose B as the payer and share "unevenly" with C only;
d) Save the receipt.
Basically, you can make any kinds of payments to offset the balances using the even/unevenly splits.
Let us know if this solves your expense splitting problems:)