Thank you @RecourseDesign @ClockworkOcean !
I was able to use your solutions with a combination of a solution in this thread ( How do I change a specific color within a texture? - #12 by Marcus-Universe )
And came up with a similar method to blend the landscape layers through annotations:
Essentially converting the annotation color to a black and white opacity mask and then blending material attributes with the opacity mask as alpha.
This is inside the Material Function: The function is just for cleaning up.
Final Result. Grass Dry is the base layer, Grass is layer one, Desert is layer 2.
PS: I should add that the Landscape Coordinates node must have an accurate mapping scale, which should match your map tile resolution.
If you’re importing your map through a heightmap. The resolution should match the heightmap otherwise, the layers will scale incorrectly across the landscape.
Thank you to both of you for so much assistance! <3
I hope this helps anyone in the future.