Adding to this.
A creative way to generate some sort of a blend.
You know the alpha of the blend occurs in situation where the value of the layer is Less than 1.
You can run a branched IF statement (apparenly you have to use Custom nodes again in ue5)
and output a texture channel (values below 1) on top of the alpha value, clamping the result in a 0 to 1 range, and using the output of the branch operation as the alpha of the lerp.
could end up being cheaper than a height blend if you utilize existing texture channels to make it.