Open up the correct graph when double clicked on.

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Importers/MasterRemapGraphImporterEditor.cs

 using UnityEditor;
+using UnityEditor.Callbacks;
 using UnityEditor.Experimental.AssetImporters;
 using UnityEditor.MaterialGraph.Drawing;
 using UnityEngine;
             window.Show();
             window.ChangeSelection(asset);
         }
+    }
+
+    [OnOpenAsset]
+    static bool OnOpenAsset(int instanceID, int line)
+    {
+        var path = AssetDatabase.GetAssetPath(instanceID);
+        ShowGraphEditWindow(path);
+        return true;
     }
 }

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Importers/ShaderSubGraphImporterEditor.cs

 using UnityEditor;
+using UnityEditor.Callbacks;
 using UnityEditor.Experimental.AssetImporters;
 using UnityEditor.MaterialGraph.Drawing;
 using UnityEngine;
         }
     }
 
-    private static void ShowGraphEditWindow(string path)
+    private static bool ShowGraphEditWindow(string path)
+        if (asset == null)
+            return false;
+
         var windows = Resources.FindObjectsOfTypeAll<SubGraphEditWindow>();
         bool foundWindow = false;
         foreach (var w in windows)
             window.Show();
             window.ChangeSelection(asset);
         }
+        return true;
+    }
+
+    [OnOpenAsset]
+    static bool OnOpenAsset(int instanceID, int line)
+    {
+        var path = AssetDatabase.GetAssetPath(instanceID);
+        ShowGraphEditWindow(path);
+        return true;
     }
 }