Very good job!

Thanks!

missed just a download and/or copy button.

The GitHub project does have an issue about adding a copy button. There’s a comment in which I link to a POC extension plugin that adds such a button.

also for theme, maybe is best to update “usage instruction”! only after some search I understood can be changed via customized menu.

Agreed. The Customizer settings are not straightforward to find. There’s another issue open to integrate the settings directly into the block editor and/or add a link to the Customizer.