Hiya!
Yes, when I made the course this wasn’t really possible. They are looking for ways to make blocks more customizable like you want and I hope to cover more hooks in a separate advanced video.
For the time being if you want a custom block you have to build it yourself.
That said, please go ask this question in WP Slack #core-editor channel and see if they have made any progress! Would love to know what you find out.
Once it’s possible I’ll prepare some material on how to do it 🙂