Looks nice. Having the immediate "Click here" that leads into the edit page with the double paned edit window is particularly cool.

Watch out with providing a hosted version of something like this with totally untrusted user input. JSON schema allows for arbitrary regexes for field validation which means a malicious user could easily bring down the site with a nasty regex[1]. Not a concern for anything privately hosted but sadly there are plenty of jerks in the world.

[1]: https://www.owasp.org/index.php/Regular_expression_Denial_of...