Alternatively, if you want to leverage tags, I would tag all shared expenses with “Split”, then use the Transaction Tracker available in Tiller Community Solutions.
Here’s a sample where I am substituting your “Split” tag with my “Charity” tag for illustration. I filter the results by a time period (I’m using Last Quarter to get a larger set of sample transactions), with this output resulting in the detail section below.
You see all results with “split” (or “charity” in my example) in the tag column, along with other details such as Account, Amount, Category, etc…
Now go to the Group By section on the right, and choose Group By “Account” This aggregates to the total paid by account towards shared transactions.
The total shared expense is $40, or $20 each. Brett has paid $30 of that, Meredith $10, and so Meredith owes Brett $10.
You could stop there, but if you want to then track Meredith’s $10 payment to Brett, I think you could tag the payment made and payment recieved with “Split.” This nets to $0, will credit Brett’s total “split” amounts to -$20 and Meredith’s to -$20. One problem: the payment is probably made in the next month, so it doesn’t aggregate neatly into the month the expenses were incurred. You could backdate the transaction date of the payment, but it’s probably not recommended to start modifying that field. Up to you. Just thought I’d share a possible solution with little custom coding.