UE4.26:How to get the direction of specific directional lights in custom node material?

This is the approach I’ve been doing to further customize things. But I’m still locked into the world’s sun light direction.

If I understood in your reply, I should be able to drive XYZ values from the RGB channels of a (thingie).
I also tried to figure out if I need a scene BP to use “get unit direction”, output a vector and use that as a variable in the material shader as the custom vector.

Yeah, I get that I don’t really need a light, just to math out 2 object’s positions in regards of each other, dot product it, normalize it and then (plug it where in the shader)? That’s the part I’m confused about. I can certainly limit (stylize) the shadow in a custom RGB channel (let’s imagine in Green channel), but then I don’t know how to add that vector into the shader itself (is it emission, roughness?). Maybe I am not picking the correct Material (it should be always unlit, and a fake vector gives the shadow mask it’s orientation in object’s VertexNormalsWS?)

Please elaborate a little bit more over the points you mentioned + my questions above.
Thank you.