I just released GMLDocMaker 0.3, with huge changes:

• Support for functions and struct documentation!
• Support for data types according to the Gamemaker/JSDoc specification, including extended tags (see project page)
• Groups all your generated documentation in an interlinked HTML project!
• Basic Markdown support for descriptions!
• Multiline descriptions
• Beta command-line support to easily update your project when making changes (without having to open the GUI)
• Rewrote parsing script in self-contained Python to speed it up

Enjoy!