Visualizer cheatsheet is good too; via https://news.ycombinator.com/item?id=22200584
https://www.janmeppe.com/blog/regex-for-noobs/ https://news.ycombinator.com/item?id=20608032
Another visualizer from the above: https://regexr.com/
You were at first excited by Rulex via this hacker news post. A small improvement, mostly seeming to add named capture groups and "variables" (really more like macros).
This page tracks a bunch of alternative syntaxes. Melody looks more like what you were thinking?
Both Melody and Rulex have playgrounds, but neither has a playground that shows the results on sample text.
Both appear written in Rust.
Super Expressive lets you programmatically create regex and is written in js. You could create a language on top of it? Its playground does include sample text.