If the former Bank Transactions and Cash Transactions forms had similarly labeled custom fields, such as Notes, the new Receipts & Payments tab’s entry forms (tagged as bank-transaction-form) will have two custom fields with the same name.
There should be some provision for consolidating content into a single field. Clearly, the user’s intent was to have a Notes field, regardless of transaction type. Although past transactions can be edited to move content from one duplicate field to another, that is an unreasonable expectation.