How to allow end-users to save progress and continue later?

By default, Apps provide end-users with a 'continue later' button:

How it works

When the end-user clicks 'continue later', they generate a URL which allows them to return to the App from wherever they left off. The end-user can either copy the URL right away or email it to themselves.

Turning this feature off

You can turn this feature off in the App Builder under Settings > Data Storage.