Working at No Ghost has encouraged me to include a few new tools into my workflow. Making landscapes outside of the unreal editor is one of them. Gaea, by QuadSpinner is the industry's leading terrain design app for VFX, Games and Virtual Production. It's pretty awesome and powered by over 150 node-based controls which makes it very easy to use and fast to see changes in real time. It has a huge selection of premade starter environments, which you can edit and build upon. Export it out as a mesh and import it into a game engine for quick and beautiful results. It's also PBR friendly and can export all the traditional Albedo, Normal, Displacement, Reflective and Occlusion, but can also be used to create more intricate masks such as splat maps, curvature, sunlight, terrain and water flow areas.
PS. The Cartography node really is cool and I'd love to make a series of maps one day with it.