Hello,

I am searching with no luck a way to divide shader into "Modules":
-Displacement Network
-Material Variant/Subset
-Material Core

So the idea is to save the geometry as USD with the displacement part of the network. Then at a later stage load the Displacement Network with a "Shader Merge"(something equivalent to "Object Merge" in SOP) and plug it into the "Material Core" from a library.

So far the only workaround to this problem I had figured out is to define my material vars in the assembly stage using hda that could change their definition with python.

Any suggestion for this?

You may be able to use "Import USD Material" VOP inside Material Library to access an already defined USD primitive from the stage.