You can edit this "code" in a text editor and some users do this, The syntax is specific to Creo Parametric as far as I know. I will warn you that it is not documented by PTC so it will involve much effort to develop it without using the record function. I am among a small group of users that would like to see PTC document the syntax but to date they have not been willing to do this. Also take not that fundamental programming concepts such as looping, search, etc. are not supported for map keys.
Check out these threads for some more tips:
https://community.ptc.com/t5/System-Administration/Mapkey-Writing-Editing-Tips/m-p/443729
https://community.ptc.com/t5/System-Administration/Notepad-User-Defined-Language-files-for-Creo-Parametric-and-Pro/m-p/451745