Playground for bikeshedding the topic token?

The Record & Tuple proposal have used a playground page to make their proposal playable in the browser. As I understand things, their playground transpiles users' script to currently supported syntax (polyfill) in the browser, https://rickbutton.github.io/record-tuple-playground/ Would this work for picking the token? I mean would it add value to trying characters combos? Instead of the `Syntax Type` dropdown in the UI, have a text input that makes some _initial validations???_ and replaces the topic token throughout the source - if we get to errors we know outright what's the holdup.