I've taken to using Markdeep [1] for this.

You write your markdown file, but add the code snippet at the bottom of yor document and save it with a .md.html extension. Then when you double-click it it opens and renders in your browser.

I save my notes in a Google Drive, and it's now replaced all the note taking apps I've tried over the years

[1] https://casual-effects.com/markdeep/