Add EnableHeightBlending property to instruct unity to not to use heightmaps.

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/Material/TerrainLit/TerrainLitUI.cs

         {
             public readonly GUIContent layersText = new GUIContent("Inputs");
             public readonly GUIContent layerMapMaskText = new GUIContent("Layer Mask", "Layer mask");
+            public readonly GUIContent enableHeightBlending = new GUIContent("Enable Height Blending", "Enables layer blending using heightmaps.");
             public readonly GUIContent heightTransition = new GUIContent("Height Transition", "Size in world units of the smooth transition between layers.");
         }
 
         public TerrainLitGUI()
         {
-            m_PropertySuffixes[0] = "0";
-            m_PropertySuffixes[1] = "1";
-            m_PropertySuffixes[2] = "2";
-            m_PropertySuffixes[3] = "3";
         }
 
         // Density/opacity mode
         // Height blend
+        MaterialProperty enableHeightBlending = null;
+        const string kEnableHeightBlending = "_EnableHeightBlending";
+            enableHeightBlending = FindProperty(kEnableHeightBlending, props, false);
             heightTransition = FindProperty(kHeightTransition, props, false);
             for (int i = 0; i < kMaxLayerCount; ++i)
             {
             EditorGUI.indentLevel++;
             GUILayout.Label(styles.layersText, EditorStyles.boldLabel);
 
-            EditorGUI.indentLevel++;
-            m_MaterialEditor.ShaderProperty(heightTransition, styles.heightTransition);
-            EditorGUI.indentLevel--;
+            if (enableHeightBlending != null)
+            {
+                m_MaterialEditor.ShaderProperty(enableHeightBlending, styles.enableHeightBlending);
+                if (enableHeightBlending.floatValue > 0)
+                {
+                    EditorGUI.indentLevel++;
+                    m_MaterialEditor.ShaderProperty(heightTransition, styles.heightTransition);
+                    EditorGUI.indentLevel--;
+                }
+            }
 
             EditorGUI.indentLevel--;
         }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/TerrainLit/TerrainLit.shader

         [HideInInspector] [ToggleUI] _OpacityAsDensity6("_OpacityAsDensity6", Float) = 0.0
         [HideInInspector] [ToggleUI] _OpacityAsDensity7("_OpacityAsDensity7", Float) = 0.0
 
+        [ToggleUI] _EnableHeightBlending("Enable Height Blending", Float) = 1.0 // Hint Unity if heightmaps are ever used
         _HeightTransition("Height Transition", Range(0, 1.0)) = 0.0
         [HideInInspector] _Height0("Height 0", 2D) = "black" {}
         [HideInInspector] _Height1("Height 1", 2D) = "black" {}
 
     #pragma shader_feature _TERRAIN_NORMAL_MAP
     #pragma shader_feature _TERRAIN_HEIGHT_MAP
-    // #pragma shader_feature _HEIGHT_BASED_BLEND // _HEIGHT_BASED_BLEND is implied if heightmap is used. 
-    #pragma shader_feature _MASKMAP0
-    #pragma shader_feature _MASKMAP1
-    #pragma shader_feature _MASKMAP2
-    #pragma shader_feature _MASKMAP3
+    // #pragma shader_feature _HEIGHT_BASED_BLEND // _HEIGHT_BASED_BLEND is implied if heightmap is used.
+
+    //#pragma shader_feature _MASKMAP0
+    //#pragma shader_feature _MASKMAP1
+    //#pragma shader_feature _MASKMAP2
+    //#pragma shader_feature _MASKMAP3
 
     #pragma shader_feature _DENSITY_MODE
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/RenderPipelineResources/DefaultHDTerrainMaterial.mat

   m_SavedProperties:
     serializedVersion: 3
     m_TexEnvs:
-    - _Control:
+    - _Control0:
-    - _HeightMap0:
+    - _Control1:
-    - _HeightMap1:
+    - _Height0:
-    - _HeightMap2:
+    - _Height1:
-    - _HeightMap3:
+    - _Height2:
-    - _MainTex:
+    - _Height3:
-    - _MaskMap0:
+    - _Height4:
-    - _MaskMap1:
+    - _Height5:
-    - _MaskMap2:
+    - _Height6:
-    - _MaskMap3:
+    - _Height7:
         m_Texture: {fileID: 0}
         m_Scale: {x: 1, y: 1}
         m_Offset: {x: 0, y: 0}
         m_Texture: {fileID: 0}
         m_Scale: {x: 1, y: 1}
         m_Offset: {x: 0, y: 0}
+    - _Normal4:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
+    - _Normal5:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
+    - _Normal6:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
+    - _Normal7:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
     - _Splat0:
         m_Texture: {fileID: 0}
         m_Scale: {x: 1, y: 1}
         m_Texture: {fileID: 0}
         m_Scale: {x: 1, y: 1}
         m_Offset: {x: 0, y: 0}
+    - _Splat4:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
+    - _Splat5:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
+    - _Splat6:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
+    - _Splat7:
+        m_Texture: {fileID: 0}
+        m_Scale: {x: 1, y: 1}
+        m_Offset: {x: 0, y: 0}
-    - _AORemapMax0: 1
-    - _AORemapMax1: 1
-    - _AORemapMax2: 1
-    - _AORemapMax3: 1
-    - _AORemapMin0: 0
-    - _AORemapMin1: 0
-    - _AORemapMin2: 0
-    - _AORemapMin3: 0
+    - _EnableHeightBlending: 1
+    - _HeightAmplitude4: 0.02
+    - _HeightAmplitude5: 0.02
+    - _HeightAmplitude6: 0.02
+    - _HeightAmplitude7: 0.02
-    - _HeightTransition: 0
+    - _HeightCenter4: 0.5
+    - _HeightCenter5: 0.5
+    - _HeightCenter6: 0.5
+    - _HeightCenter7: 0.5
+    - _HeightTransition: 0.004
+    - _Metallic4: 0
+    - _Metallic5: 0
+    - _Metallic6: 0
+    - _Metallic7: 0
+    - _OpacityAsDensity4: 0
+    - _OpacityAsDensity5: 0
+    - _OpacityAsDensity6: 0
+    - _OpacityAsDensity7: 0
-    - _SmoothnessRemapMax0: 1
-    - _SmoothnessRemapMax1: 1
-    - _SmoothnessRemapMax2: 1
-    - _SmoothnessRemapMax3: 1
-    - _SmoothnessRemapMin0: 0
-    - _SmoothnessRemapMin1: 0
-    - _SmoothnessRemapMin2: 0
-    - _SmoothnessRemapMin3: 0
+    - _Smoothness4: 0
+    - _Smoothness5: 0
+    - _Smoothness6: 0
+    - _Smoothness7: 0
-    - _TexWorldScale0: 1
-    - _TexWorldScale1: 1
-    - _TexWorldScale2: 1
-    - _TexWorldScale3: 1
-    - _ZTestDepthEqualForOpaque: 4
+    - _ZTestDepthEqualForOpaque: 3
     - _ZTestGBuffer: 4
     - _ZWrite: 1
     m_Colors: