I was working with a map in the world editor and suddenly the grass, without any warning, disappeared.
In the level 'Scene Tree' (in the editor). The entity is called groundcover but, depending if you used another level as base, it could have a different name (like grass, or etc)
The name is indifferent, you call it 'birthday cake' but it all depends from what settings you have there If you see it's parameter, you can see you can tune quite lot of stuff. The bare minimum to have grass is to set up the texture correctly, and assign the correct 'Terrain Layer' to it. If you never used this, I'd advice checking how official maps do it, and perhaps copy their settings.
