Yeah it’s tricky, one has to keep in mind that all of these are stacking heightmaps, and the min/max/additive/blend controls how to they mix, also the alphas on the actual layers. For instance if you have a top most layer (above the water layer) with alpha layer 1.0, then it will “block” water in some cases, while, like 0.5 will let it through
AFAIK, to have lakes etc work properly you need to have that heightmap in your water landscape layer, and within the ocean spline, lakes will work relative to that.
If you want shores etc that are not capped by the ocean you can but them in a top layer, just make sure you’ve scaled it’s height if you import a height map, it’s very tricky to make lakes work on that layer however.
Seems like a best solution would be to split imported heightmaps into one shore aspect that lives in a separate layer, and everything on the ocean landmass into another that you put on the water layer, then you dont have to fiddle with your spline and lakes work. Getting that setup isn’t exactly the easiest tho so I hope there’s some better work flow.
I also don’t know how you affect terrain on island and still are able to use lakes etc, you cant really but height in the water layer, and if you put it somewhere else the lakes won’t react correctly, maybe there some way to link terrain layers to an actor? Would be great if you could have a layer just going on top an island