It seems to me you are looking for a syntax highlighter in a note taking app. Which modern language are you looking for?

There are encrypted backups. Actually, backups are encrypted by default.

Notesnook also works offline by default so there's no need for a special mode. It's also, obviously, local-first since everything gets encrypted on your device. We don't have a lot of options there.

What "might be better" in the editor?