@Digital-X dont mess with tree amount and there is reason why you dont want too
The grass brushes are simple plane model flat
The other plant stuff like trees is actual 3d model remember i talked about above to manny 3d models throw at engine will overload it and cause crap fps and fps dips
You can also create ur own grass brushes by simply creating new section in above coding,a grass xml for it which would sit in classes>>grass folder
then a simple flat 3d model of grass then texture it....grass doesnt have a billboard so no need to worry about that
Careful too the editor is touchier than a woman at times ...screw with the wrong thing and it may slap ya then say nope done working for you at this point and suddenly start crashing...tread carefully when messing with anything...i always create a new folder in say plant folder and back up any files im going to mess with...i would do this always incase you bugger something you dont have to scrap the whole editor and reinstall it