So I have noticed that there is posibility to make average normals similar like in YAVNE addon but how to use that on selected faces? Weighted normal editor doesnt work on selected faces which is my problem.!
Into Normals panel, you choose to set a strength (Weak, Medium or Strong) for selected faces.
But, you only see the result by enabling autosmooth and using a Weighted Normal modifier with Face Influence option ON.