Landscape material manipulation

Well in short, landscape layer materials are a LIST

LISTs require common type of CRUD operations (create, read/use, update and delete)

I have some 12 or more sands, leaves, dirt, grass foliage etc in the list

BUT I have an overlay texture (2D as material) that was a photo from the air that shows me where shoud what type od material come - i.e. where is grass, path, road, bushes, trees etc

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QUESTION: Is there a sane/normal way to add this material to the list of landscape materials & then simple OVERWRITE it with paint in landscape mode that adds correct paint book over it?

Thank you in advance

(it is mind boggling that SIMPLE stuff is so difficult to do in UE…) eh eh