I’ll start with the short version, asking how to do the following specific action. Where I have the landscape for position x3_y0, I want to import a second landscape for x3_y0, and have both exist simultaneously. Is there a way to do that?
EDIT: SOLUTION.
The problem wasn’t that UE4 was not allowing me to import several sets of the same tiled landscape with different heightmaps into one level, it does that by default. it was because my heightmap for the water’s surface was solid black, to give me a flat plane. For some reason, the RAW file in 8 bit format just doesn’t work with UE4 when all black, returning a report about a filesize error. Rendering the same file as a RAW 16 bit cleared the issue and imported without a problem.