The doc that comes with GameGuru only has a generic overview of the language, and not GameGuru specific commands.

You might have seen these already:
http://steamcommunity.com/app/266310/guides/#scrollTop=0

https://forum.game-guru.com/thread/208970

The only thing that would be newer is the ones listed in the Global.lua file.
In the announcements when the release the commands, will also be there definition. In the Game Guru main folder there is a file call changelog.txt, and this will also have the most current info available.

Hi Myke, and thank you for your help.

I couldn't find it in any of the commands, so I am guessing the answer the answer is no, but is there any way to clone or copy an entity with lua? I wanted to try and procedurally generate trees and rocks.

If you mean lua commands, there is a thread in the scripting forums with most commands listed. You can also use the global file to find all the commands so far. Other than that, more specific stuff for GG in editor and test games can sometimes be difficult to find and as you say not well documented yet. By following Lee's blog regularly I tend to pick up on most new things, but you can forget and have some trouble finding the blogs referring to it at times Not ideal, but until GG is more finished I doubt we will see much time put into docs.

Edit - No. You can't clone or copy in GG as yet at all beyond the actual editor. I have asked for a command like this several times. It would be very useful.

That would be a useful command. Duplicating entities via LUA.

Cloning entities are planned for Lua scripting, just not in yet.
Somebody in the scriptboard is working on this I believe on there own.