Well I recently got all of the particle functions and some other ones documented on the Wiki.
http://enigma-dev.org/docs/Wiki/Particle_FunctionsI noticed we have finally reached the point that most of the GM functions are documented. About 80% to 90% of the basic standard GM functions are now documented, the two left columns on the following Wiki page.
http://enigma-dev.org/docs/Wiki/Function_DocumentationDrag and Drop Actions have also been entirely documented for some time.
http://enigma-dev.org/docs/Wiki/ActionThese are documented with information about their parameters, return types, data types, and even provide example code. This was a lot of work, but in no way is the Wiki done, it needs to be maintained and there are still new Studio functions to add and document. The Wiki is also generating between 20 and 100 visits to the website each day, these are most likely coming from Google hits as the result of people searching for GM functions, see the following.
https://www.google.com/#q=d3d_model_createYou can see the ENIGMA docs linked right below the GM Studio doc pages. This however is also just the main page, and does not indicate the hits being generated by the sub pages of the Wiki which could also make it much higher.
I want to take the opportunity to thank some people.
Harri - For a lot of the original function docs I used to convert into the new format.
X - He started out with the file functions and documented a bunch more and also converted some tutorials
Josh/Ism - Pretty much all of the documentation on ENIGMA's internals
Polygone - For making sure links stay up to date and doing some docs
Others - People who I might be forgetting and that came before me here.
At any rate, we are now the largest online and offline source of libre/free documentation for Game Maker. Their Wiki has been taken down, see for yourself, it redirects to the knowledge base now.
http://wiki.yoyogames.com