I have found the file in my ProgramData folder on Windows. The folder is usually hidden, so the way to go is:

C:\ProgramData\MA Lighting Technologies\grandma\gma2_V_3.1.2\plugins

If you're running another version number, the folder is named differently ofcourse.

Don't know if there is an easier way to find it, but this worked for me! In the plugin_1 file are some demo scripts and is a simple API. As far as I know, the functions described in this example are the only GMA functions available in LUA so far.

With Regards,
Harm Wellink