Interesting. Editing and designing terrains from scratch in World Creator. Seems to work only on tiles and not on a planetary scale though.
The thing about trying to create a terrain on a planetary scale is it's really very difficult to export the data (terrain) once you have created it. You either get fairly low detail, or a huge, huge amount of data. The best way to manage it is to generate the terrain in the same app you render it, like Terragen. ;)
I tried some world machine stuff a few years ago but found the creation process, and than finalization in Terragen slow over just creating in Terragen.