Scratch supports Korean, but Scratch benefits from using JSON instead of bytes or code points to serialize programs, which allows the user to change their display language (similar to how hard tabs let users set indentation size).

There's probably a lot of reasons why non English programmers stick with English keywords, beyond just language/tooling support. Learning new keywords is already part of learning a programming language, and much of the documentation and resources available for languages and libraries are only in English. ASCII-only strings are still ubiquitous in software, like URLs and usernames. And in international teams, English is the go-to lingua franca.

Could this change with LLMs? Maybe, but most code in its training data is in English, so LLMs likely work most effectively in English.