title: How to make a Unity Editor member variable persistent? (member of Editor, NOT target class)
body: <p>I know how to use serializedObject.FindProperty() on a member of the target class, but I just want to make one of the Editor's member variables persistent. Googling onlyshows the cases for the target class.</p>
  <pre><code>    public class MyEditor: Editor
      {
          [SerializeField]
          int myInt = 1;
          ...
      } 
     public override void OnInspectorGUI()
     {
        myInt = EditorGUILayout.IntField(myInt);
        ...
     }
  </code></pre>
  <p>I can set a value for myInt in the Inspector, but when I leave and then return to the Editor, myInt is reset to its default value. I know I could simply put myInt in the target class, but I need the variable in this class.</p>