Second texture for the slope on the terrain

Unity Engine
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1

tell me how to do the following - use the standard terrain shader but add another texture to it that will be displayed on the surface with an angle of more than 30 degrees, how to do this?
(URP)

2

I decided to copy the contents of the standard terrain shader and make my own changes to it, but I add the initial fields like

[HideInInspector] _MainTex("BaseMap (RGB)", 2D) = "grey" {}
_SlopeTexture("Slope Texture", 2D) = "white" {} // add <----------------------------------------
HideInInspector] _BaseColor("Main Color", Color) = (1,1,1,1)

but this field is not visible in the inspector, why?
I would like to add some changes if possible…