Duplicating a transaction allows you to create a duplicate of an existing transaction that you can then either leave as an exact duplicate or modify to change some elements of it. This guide explains how to duplicate transactions and also why the transaction date sometimes gets changed while duplicating transactions.
You can duplicate transactions in two ways:
swipe right on the transaction to reveal Duplicate button and click it,
bring up the contextual menu and select Duplicate.
You'll then be presented with a new transaction window, pre-filled with details of the original transaction. You can either leave it as it is and save the transaction or change some details of it before saving.