Except this whole design falls apart when customer pays 100,000 but you see on bank statement 99,900 because the bank took 100 in bank fees. Or when portion of the amount is for something entirely else. Or when amount paid is actually higher than the amount of all invoices because the reminder is some sort of prepayment for future work.
This is why Manager has never gone this direction. You think it solves one problem, then it creates another problem elsewhere. You end up with more complicated system for no gains.
Here is my thinking… if customer sends you remittance advice which indicates how the amount paid for invoices should be split, allocate payments against individual invoices. If customer doesn’t send you remittance advice, just allocate the amount paid to accounts receivable account without specifying an invoice (let Manager do the splitting). At no point do you need to know balances due on individual invoices.
If customer remittance advice is a lot of invoices and you really don’t want to enter those invoices (and amounts) individually, there is a shortcut.
When you view their customer statement in Manager, there is Copy to button.
This will let you copy all invoices from customer statement with their balances to new bank/cash transaction.
Here you can easily remove invoices which haven’t been paid by clicking on X button or change the amount if the amount paid was actually lower.