Minecraft World Editor program?

For Minecraft there's the World Editor with which you can change the terrain in the game. So with the // wall and such. This is very practical, but if you e.g. If you want to create an entire mountain range, this is very time-consuming. Hence my question whether there's a program outside of Minecraft with which you can edit existing worlds and, among other things, create mountains and waters with little effort. Terraforming, so to speak!

WorldPainter would be.