Use a separate window for transaction edits that is visually different from the transaction register. It could have all the existing navigation shortcuts or not, but it should be designed to clarify the differences from the register view caused by the need for the 'extra' account to complete double entry information, which defaults, of course, to the current account. Since the default account could be shown in a separate box, it would not be in the way when a new split line is added. When splits are created, extra boxes or lines appear for the additional number, action, memo, amount and account. Space could be provided for existing or possible additional features like reconcile date, links to images, etc. which may not need to be shown in the register itself. The recent tab entry discussion may be resolvable in this scenario.