As of version 1.2.1214, GameMaker Studio can display your custom script arguments in IntelliSense. If not configured, GameMaker Studio’s editor will not display arguments for scripts while typing code.
To add intelligent code completion to scripts, simply add /// at the top of your script, then define the function name and arguments.
Do not use spaces between the script name and the leading parenthesis, or between arguments.
It takes just a few seconds to improve your scripts by adding intelligent code completion.