Nothing so far has resulted in anything showing up in the editor once I reopen it.
Do I need to do anything to the terrain besides creating a new level, creating a terrain with a base material and saving?
The editor copies the "terrain.data" file in several different locations. The "original" version that is open by the editor and copied everywhere else is here:
\Divinity - Original Sin\Data\Editor\Mods\ModName\Levels\LevelName\Terrains
You should NOT edit the copy that is here:
\Divinity - Original Sin\Data\Mods\ModName\Levels\LevelName\Terrains
