Currently there isn't a way to view contents of a terrain. This makes it very difficult to replace or remove data. There is a remove feature tool but you have to know which features are in a terrain to remove them.

I am proposing an empty terrain tool similar to InRoads where the contents of the terrain are emptied and the terrain is not deleted. Features can then be re-added. This will allow all links to the terrains to hold. i.e, complex terrains, clipped terrains, corridors and drainage structures.