A few people have mentioned the compose key as a way to insert Unicode characters system-wide. I also really like Espanso[0]: You can use it to replace any type

A few people have mentioned the compose key as a way to insert Unicode characters system-wide. I also really like Espanso[0]: You can use it to replace any typed string with anything else, it even supports forms and executing scripts / shell commands. There's tons of fancy stuff you can do with it, but just mapping something like \alpha or :a* to ɑ is easy too. (For greek characters, there's a package that uses a syntax like \alpha\) [0]: https://espanso.org/ https://espanso.org/