There are two ways to back up the data in this app.
1. Android backup and restore (official feature)
This app supports Android's official backup and restore feature. Enable Google backup from the Settings app on your device. When you switch devices, set up the new device with the same Google Account and your data will be carried over.
2. Export and restore backup data from the app
On the Other screen in the app, go to Data backup / Restore and tap Export backup data to save your data as a CSV file.
You can restore the exported CSV file at any time by selecting Restore backup data on the same screen. This also works for transferring data when you switch devices.