Invoice <-> Account Link or Identifier
I see on the roadmap a future commitment to an "Invoice payment" feature. Technically this can be accomplished presently with the moneyTransactionCreate mutation, so long as you know which accounts receivable account pertains to the invoice to be paid. And herein lies the problem: I can see no way to identify which account of subtype.value=RECEIVABLE_INVOICES pertains to each invoice. Adding the ID of said account to the Invoice type could allow developers to pay invoices without a full-fledged solution.