World composition, Large Landscapes and multiple biomes how to use splat map or equivalent

Okay so first of all i have created a huge landscape inside World machine, 32X32KM also i have multiple bomes ie canyons, sandstone, jungle, big lake, snowy mountains etc, now a simple splat map will not work as it will cover the whole terrain based of slope or height.

question is how do i get a splat map working efficiently for all biomes, currently i have made a splat map for each biome 4 materials per biome, but how do i get this in the engine as i have needed to split the splat map into individual channels so i can import them as (layer) tiles on importf9e06a138c201cd873b798eb08bc205c02e32c90.png
here is my current setup for world machine this will let me export each mask for individual layers i create inside unreal engine and in the top left corner you can see i have used the layer generatior to mask out a specific part of the terrain for the mask and then ive subtracted another layer generator away for it after to remove parts of the white in places i dont want the mask to be
as you can see my graph is kinda complex the groups on the left are simply biomes for the terrain all blended to gether and the groups on the right are splat>rgb split>SOLO masks

im looking at finding a reasonable way to do this

Still waiting for an answer on this topic