Accessing one expression library functions from another expression lib

I don’t think so.

The expression language is mostly a subset of JavaScript, so I would just use an editor with support for that. The main difference is that expression language is just expressions, not statements. Don’t try to use things like if or function(), you need to stick to arrow functions (e.g. (x, y) => x + y). One addition to the e-lang that is not in JavaScript is the match operator. You might find that useful if you have to do a lot of conditionals.