This feature is currently only available on the full web version, not the mobile app. The export button is now located in the top right of the main Transactions screen.
Click on the downward arrow icon to download a .csv file of the transactions.
Note that when the page loads it will now initially bring up the most recent 100 transactions. Historic transactions will then continue to load as you scroll down, though if you attempt to export the transactions to csv without scrolling it will only export the first 100 transactions.
If you need to export more than this you will first need to scroll down to the bottom of the list (or at least as far as the earliest date you require) before exporting. This also applies when exporting the results of a filtered search if more than 100 entries are returned.