Unfortunately, you cannot. These are all limitations of the Tools/Surface Painter.
The various tools each have a certain amount of Surfaces you can specify. For example, Walls have 3, one of which is the Edge Surface, and it applies to all Wall edges (top, bottom, start, end). It is not possible to set these edges Surfaces individually.
The only element type where each individual face of the element can be set to a different Surface is the Morph Tool.
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