What kind of MapEditor is this? (Octopath Traveler)

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So, i really want to make a top down turn based rpg in Unreal and in saying those words the first recent game that comes to mind is Octopath Traveler by Square-Enix. Now, i imagine that this tool was made in-house specifically for this project but is there any tutorial that would help me to create a landscape like that? (The landscape seems to be divided in small cubic segments and this grass texture and rock texture looks very good for me, i wonder how to make something like it…). And as always, thank you very much!