What approach do you usually use to create a terrain and scenes for your games,
is it scene editor + terrain editor in SDK or something else?
You can use Blender which has a landscape addon.
You can then convert that landscape into a heightmap and use it in games.
This page is old so you have to learn where everything has moved but its not to difficult.
You can also create the landscape manually in blender if you want.
I have created my own in game map editor (for my voxel-based terrain) done with Lemur GUI and I have a bunch of scripts to help with plotting objects (trees, plants, fences, rocks,…) on the terrain.
I use blender just for creating and exporting models.
i also have own editor for custom terrain.
You can look at JME SDK sourcecode of Editor and just copy paste code and make yours one (if it gonna be using default JME terrain)
You should use SDK one if you create default easy game.
But for advanced games you will anyway need a lot of things that default editor do not support so you would end making custom one(or doing solutions like Blender solution one). like @Ali_RS mentioned custom editor might provide more tools than just for a terrain.
its hard to predict what game dev gonna need.
So in short, it depends if you create easy or advanced game
Thanks all for your replies