How to make terrain partially transparent (lower opacity)

Wehave you read this here? https://answers.unity.com/questions/1162779/unity-5-transparent-terrain-shader.html it replaces the standard terrain shader

Edit

as mentioned in the above article, copy paste this in a new created shader file

 Shader "Terrain/Transparency" 
  {
       Properties {
           [HideInInspector] _Control ("Control (RGBA)", 2D) = "red" {}
           [HideInInspector] _Splat3 ("Layer 3 (A)", 2D) = "white" {}
           [HideInInspector] _Splat2 ("Layer 2 (B)", 2D) = "white" {}
           [HideInInspector] _Splat1 ("Layer 1 (G)", 2D) = "white" {}
           [HideInInspector] _Splat0 ("Layer 0 (R)", 2D) = "white" {}
           [HideInInspector] _Normal3 ("Normal 3 (A)", 2D) = "bump" {}
           [HideInInspector] _Normal2 ("Normal 2 (B)", 2D) = "bump" {}
           [HideInInspector] _Normal1 ("Normal 1 (G)", 2D) = "bump" {}
           [HideInInspector] _Normal0 ("Normal 0 (R)", 2D) = "bump" {}
           // used in fallback on old cards & base map
           [HideInInspector] _MainTex ("BaseMap (RGB) Trans (A)", 2D) = "white" {}
           [HideInInspector] _Color ("Main Color", Color) = (1,1,1,1)
       }
   
       CGINCLUDE
           #pragma surface surf Lambert alpha vertex:SplatmapVert finalcolor:SplatmapFinalColor finalprepass:SplatmapFinalPrepass finalgbuffer:SplatmapFinalGBuffer
           #pragma multi_compile_fog
           #include "TerrainSplatmapCommon.cginc"
   
           void surf(Input IN, inout SurfaceOutput o)
           {
               half4 splat_control;
               half weight;
               fixed4 mixedDiffuse;
               SplatmapMix(IN, splat_control, weight, mixedDiffuse, o.Normal);
               o.Albedo = mixedDiffuse.rgb;
               o.Alpha = mixedDiffuse.a;
           }
       ENDCG
   
       Category {
           Tags {
               "Queue" = "Transparent+1"
               "RenderType" = "Transparent"
           }
           // TODO: Seems like "#pragma target 3.0 _TERRAIN_NORMAL_MAP" can't fallback correctly on less capable devices?
           // Use two sub-shaders to simulate different features for different targets and still fallback correctly.
           SubShader { // for sm3.0+ targets
               CGPROGRAM
                   #pragma target 3.0
                   #pragma multi_compile __ _TERRAIN_NORMAL_MAP
               ENDCG
           }
           SubShader { // for sm2.0 targets
               CGPROGRAM
               ENDCG
           }
       }
   
       Dependency "AddPassShader" = "Hidden/TerrainEngine/Splatmap/Diffuse-AddPass"
       Dependency "BaseMapShader" = "Diffuse"
       Dependency "Details0"      = "Hidden/TerrainEngine/Details/Vertexlit"
       Dependency "Details1"      = "Hidden/TerrainEngine/Details/WavingDoublePass"
       Dependency "Details2"      = "Hidden/TerrainEngine/Details/BillboardWavingDoublePass"
       Dependency "Tree0"         = "Hidden/TerrainEngine/BillboardTree"
   
       Fallback "Diffuse"
  }

create a new Material and asign this shader to it. under the Terrain Settings, you’re able to asign the material under the Setting: Material to the Terrain.

now to paint Transparency to your Terrain you need to have a Transparent Image, this you asign just as normal teztures to the Terrain. the Trick is now, that your other Textures don’t have a Alpha Channel, unless you want the texture to have Transparency!

If you don’t want to have Transparency om the Textures you need to delete the Alpha Channel in a 3d Party Programm like Photoshop, Gimp.