Splat Map with transition texture?

Hi! I have been following catlikecoding's tutorial on this terrain editor and i need help figuring out how or where i would add a texture to the shader in order to transition from one texture to the other. At the moment it just lerps between the two textures which looks not like the style i am going for.

This is how it looks right now

This is the result of that transition texture i'd like to implement where the texture blends a bit more uneven, likely achieved through an extra noise texture? (picture from endless legend)

this is the code i have from catlikecoding

 Shader "Custom/TerrainShader"
 {
     Properties {
         _Color ("Color", Color) = (1,1,1,1)
         _MainTex ("Terrain Texture Array", 2DArray) = "white" {} //add our epic 2D texture arrays
         _GridTex ("Grid Texture", 2D) = "white" {}
 
         _BumpMap ("Normal Map", 2D) = "bump" {}
         _NormalScalar ("Normal Scalar", Range(0,100)) = 0.01
         _NormalWeight ("Normal Weight", Range(0,5)) = 1
 
         _Glossiness ("Smoothness", Range(0,1)) = 0.5
         _Specular ("Specular", Color) = (0.2, 0.2, 0.2)
         _BackgroundColor ("Background Color", Color) = (0,0,0) //color unexplored areas will be tinted to
         [Toggle(SHOW_MAP_DATA)] _ShowMapData ("Show Map Data", Float) = 0
     }
     SubShader {
         Tags { "RenderType"="Opaque" }
         LOD 200
         
         CGPROGRAM
         #pragma surface surf StandardSpecular fullforwardshadows vertex:vert
         #pragma target 3.5
 
         #pragma multi_compile _ GRID_ON
         #pragma multi_compile _ HEX_MAP_EDIT_MODE
         #pragma shader_feature SHOW_MAP_DATA
 
         #include "HexMetrics.cginc"
         #include "HexCellData.cginc"
 
         UNITY_DECLARE_TEX2DARRAY(_MainTex);
 
         struct Input {
             float4 color : COLOR;
             float3 worldPos;
             float3 terrain;
             float4 visibility; //float 4 instead of 3 to accomodate exploration state as well
 
             #if defined(SHOW_MAP_DATA)
                 float mapData;
             #endif
         };
 
         void vert (inout appdata_full v, out Input data) {
             UNITY_INITIALIZE_OUTPUT(Input, data);
             //data.terrain = v.texcoord2.xyz;
 
             float4 cell0 = GetCellData(v, 0);
             float4 cell1 = GetCellData(v, 1);
             float4 cell2 = GetCellData(v, 2);
 
             data.terrain.x = cell0.w; //terrain type stored in last component w
             data.terrain.y = cell1.w;
             data.terrain.z = cell2.w;
 
             data.visibility.x = cell0.x; //cell visibilty stored in first component x
             data.visibility.y = cell1.x;
             data.visibility.z = cell2.x;
             data.visibility.xyz = lerp(0.25, 1, data.visibility.xyz); //make it not fully dark
             data.visibility.w = cell0.y * v.color.x + cell1.y * v.color.y + cell2.y * v.color.z; //exploration state
 
             #if defined(SHOW_MAP_DATA)
                 data.mapData = cell0.z * v.color.x + cell1.z * v.color.y + cell2.z * v.color.z;
             #endif
 
         }
 
         half _Glossiness;
         fixed3 _Specular;
         fixed4 _Color;
         sampler2D _GridTex;
         half3 _BackgroundColor;
 
         sampler2D _BumpMap;
         fixed _NormalScalar;
         fixed _NormalWeight;
 
         //make texture coordinates, sample array, modulate sample with splat map
         float4 GetTerrainColor (Input IN, int index) {
             float3 uvw = float3(IN.worldPos.xz * (2 * TILING_SCALE), IN.terrain[index]); //coord scaled down so texture doesnt tile too often
             float4 c = UNITY_SAMPLE_TEX2DARRAY(_MainTex, uvw);
             return c * (IN.color[index] * IN.visibility[index]); //color can be treated as array as it represents 0 = r, 1 = g, etc
         }
 
         void surf (Input IN, inout SurfaceOutputStandardSpecular o) {
             fixed4 c = 
             //last coordinate is texarray index
                 GetTerrainColor(IN, 0) +
                 GetTerrainColor(IN, 1) +
                 GetTerrainColor(IN, 2);
 
             fixed4 grid = 1;
             #if defined(GRID_ON)
                 //the whole 5sqrt3, 20sqrt3 hexagon thing to calculate grid tex size correctly
                 float2 gridUV = IN.worldPos.xz; 
                 gridUV.x *= 1 / (4 * 8.66025404); //inner radius  of cells four times in order to move two cells to right
                 gridUV.y *= 1 / (2 * 15.0); //frwd dist between cell centers is 15
                 grid = tex2D (_GridTex, gridUV); //gridUV insteadof IN.worldPos.xz
             #endif
 
             float explored = IN.visibility.w;
             o.Albedo = c.rgb * grid * _Color * explored;
             #if defined(SHOW_MAP_DATA)
                 o.Albedo = IN.mapData * grid;
             #endif
             o.Specular = _Specular * explored;
             o.Smoothness = _Glossiness;
             o.Occlusion = explored; //without this the surface specular has a fresnel effect which we dont want
             o.Emission = _BackgroundColor * (1 -  explored);
             o.Alpha = c.a;
 
             //really ugly add
             o.Normal = UnpackScaleNormal(tex2D(_BumpMap, _NormalScalar * IN.worldPos.xz), _NormalWeight);
         }
         ENDCG
     }
     FallBack "Diffuse"
 }