Landscape Height Transition

Hello,

im wondering how to get a good transition between two textures based on a height lerp in a slope mask from world machine.
I tried different things like slope mask from world machine and procedurally slope mask in ue4. Nothing worked very well.
The only thing that worked quite well is when i paint my landscape layer based on height lerp manually and smooth some parts out and then i get good transitions. but i really dont want to paint 2x2km².

Here are some screenshots:

Slope mask from world machine:
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Slope mask as image:
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procedural slope mask procedurally generated in ue4:
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Slope mask node setup:
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Painted manually and smoothed out (Thats the transition that i would like to have)
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I would prefer to have a solution for good transitions when i import the slope mask from world machine instead of having a solution for for the procedurally generated slope mask in ue4 because i like the slope mask from world machine much more.

Thanks,

Someone has an idea ?