From the “Other” screen in the app, tap “Back up Data.” Then, tap “Output Data” and tap “Write a File” to instruct the app to output a CSV file and open the send email screen. This allows you to save a data backup by sending it to your own email address.
In addition, you can use iCloud Backup by using the paid premium service. By using this feature, you can easily save and restore data without saving it through email each time.