Generative seamless textures across multiple planes?

So that was great advice, and I've gotten this working really well for my purposes now. I added a couple lines of code to an answer posted by user "Owen Reynolds" on this question so that I could manually tweak the scale of the world-aligned repeating texture from the GUI side.

Here's the full code of the working shader, hope it helps somebody else:

 Shader "custom_shaders/Transparent_Diffuse_World_Aligned" {

Properties { _Color ("Main Color", Color) = (1,1,1,1) _MainTex ("Base (RGB) Trans (A)", 2D) = "white" {} _Scale ("Texture Scale Multiplier", Float) = 0.1 }

SubShader { Tags {"Queue"="Transparent-101" "IgnoreProjector"="True" "RenderType"="Transparent"} LOD 200 Cull Off Fog {Mode Off}

 CGPROGRAM
 #pragma surface surf Lambert alpha
 
 sampler2D _MainTex;
 float4 _Color;
 float _Scale;
 
 struct Input {
     float2 uv_MainTex; // unused
     float3 worldNormal;
     float3 worldPos;
 };
 
 void surf (Input IN, inout SurfaceOutput o) {
   // Guess correct planar map from normal. 0.5 is an arbitrary cutoff
   float2 UV;
   // NOTE: assuming no bottom-facing, otherwise use abs()
   if(IN.worldNormal.y>0.5) UV = IN.worldPos.xz; // top
   else if(abs(IN.worldNormal.x)>0.5) UV = IN.worldPos.yz; // side
   else UV = IN.worldPos.xy; // front
 
   // 0.1 is an arbitrary x10 texture size scale 
   half4 c = tex2D (_MainTex, UV* _Scale)* _Color;
   o.Albedo = c.rgb;
   o.Alpha = c.a;
 }
 
 ENDCG

}

Fallback "Transparent/VertexLit" }