Chaining for detailing
The "Create terrain" component outputs a mesh terrain.
The "Edit terrain" takes a mesh terrain and again spits out a mesh terrain.
So its possible to feed the mesh output from one component into another. This is chaining.
But if you create a terrain from a set of curves why would you want to edit it right after you created it?
Why would you want to chain these components?
The answer is that you often create large terrains at one resolution and then refine it in one small area at a finer detail. By chaining you can concentrate your edits to only a small area of the large terrain.
This can improve performance and quality of your workflow a lot.
To do this you simply input the output from either the "Create Terrain", "Edit Terrain" or "Flatten Terrain" component into another "Edit Terrain" or "Flatten Terrain" component.
And as the "Edit Terrain" component outputs a new mesh terrain you can potentially add as many "links" to this chain as you want untill you have the terrain detail you want
Actually there no more to it than that. So thats it. Go chain some terrains!