It's not so obvious! We're going to need to provide some really solid examples for this.
Yes, that makes a lot of sense. We know linking submissions to registration/creation forms is a painpoint and one thing we're planning to do soon is to include the created Entity in the data exports (Github issue). We will likely do the same with repeat instances though perhaps in a later release.
This is also something we plan to eventually provide directly from Central but we don't have a timeline for it currently.
We have just published a new Collect beta with offline support for Entity creation and update. You can find out more and see some sample forms in the beta release announcement.