Try & Error

[요약]

1) Tags { "Queue"="Transparent" "RenderType" = "Opaque" }

2) #pragma surface surf Lambert alpha

----------------------------------------------------------------------------

Three steps:

Add objects rendered with this shader to the Transparent queue by adding “Queue”=“Transparent” to the subshader’s Tags list.
Add “alpha” to the surface function declaration, after the lighting function declaration, so the line becomes “#pragma surface surf Lambert alpha”
Actually set the alpha to something in the surface function, i.e. set o.Alpha = whatever you want.
I have done these modifications and used the _ColorTint’s alpha channel in the example. Then the shader becomes this:

Shader "-smn-/GlowingBorder" {
    Properties {
       _ColorTint("ColorTint", Color) = (1,1,1,1)
       _MainTex("Main Texture", 2D) = "white" {}
       _BumpMap("Normal Map", 2D) = "bump" {}
       _RimColorOuter("Rim Color Outer", Color) = (1,1,1,1)
       _RimColorInner("Rim Color Inner", Color) = (1,1,1,1)
       _RimPowerOuter("Rim Power Outer", Range(0.0, 7.0)) = 3.0
       _RimPowerInner("Rim Power Inner", Range(0.0, 20.0)) = 3.0
    }
    SubShader {
       Tags { "Queue"="Transparent" "RenderType" = "Opaque" }
 
 
       CGPROGRAM
       #pragma surface surf Lambert alpha
 
       struct Input {
         float4 color : COLOR;
         float2 uv_MainTex;
         float2 uv_BumpMap;
         float3 viewDir;
       };
 
       float4 _ColorTint;
       sampler2D _MainTex;
       sampler2D _BumpMap;
       float4 _RimColorOuter;
       float4 _RimColorInner;
       float _RimPowerOuter;
       float _RimPowerInner;
 
       void surf (Input IN, inout SurfaceOutput o) {
         IN.color = _ColorTint;
         o.Albedo = tex2D(_MainTex, IN.uv_MainTex).rgb * IN.color;
         o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap));
 		 o.Alpha = _ColorTint.a; // For example. Could also be the alpha channel on the interpolated vertex color (IN.color.a), or the one from the texture.
		
         half rimOuter = 1.0 -saturate(dot(normalize(IN.viewDir), o.Normal));
         half rimInner = saturate(dot(normalize(IN.viewDir), o.Normal));
         o.Emission = (_RimColorOuter.rgb * pow(rimOuter, _RimPowerOuter)) + (_RimColorInner.rgb * pow(rimInner, _RimPowerInner)) ;
       }
       ENDCG
    } 
    FallBack "Diffuse"
}

[출처] https://discussions.unity.com/t/how-can-i-add-alpha-channel-to-this-shader/100942

[링크] https://liveupdate.tistory.com/308