I can bet you within 6 months (perhaps more) , you won't have an editor for terrain as complete as this one and as powerfull !

I meaned official in 3DGS , but fisrt a complete terrain editor, and
in game editing for 3DGS .. when ???

For it's price , i agree 3DGS is a great valuable enought powerfull 3D egine

Now this Ogre3D plugin is powerfull indeed , lot lot of geometry :
massive , it can be mesh instancing or other technique what matters
is to have such engine feature and ease of use !

I just said , it's great for full terrain vegetation and it's open source ,
that's all.

Now some engines like Unity , already do excellent results or terrain vegetation and real time editor