[endgame]

I've been using Dhall ( https://dhall-lang.org ) and it does this. But it goes a step further: because `dhall format` defines the canonical form of any dhall code, it does the unicode substitution for you. So you get convenient entry with a normal keyboard, plus nice unicode symbols in code.

[lizmat]

This is something Comma, the IDE for the Raku Programming Language, also does: https://commaide.com