Custom Inspector: nested lists not serializing with Editor.target

Hello. I'm trying to make a custom inspector, which let me show Lists of Lists on my way. I have a problem with serialization those, because when I hit play or exit Unity I lost my inpected data. I know that Unity doesn't serialize nested Lists, so I've tried many solutions posted in other questions or forums (like this: http://answers.unity3d.com/questions/784507/add-list-to-serialized-list.html). Unfortunately, any of those solutions doesn't work and I don't have any more ideas how to fix it. Can you help me?

I don't want to support multi-editing, so I didn't use SerializedObject/Property and using those is difficult to work with Lists (even more with nested lists). To watch if something was serialized or not I got a counter .Count.

Here's my code (you can copy-paste it, it will work): Main class:

 [CustomEditor(typeof(GeneratorData))]
 public class GeneratorDataEditor : Editor
 {
 
     GeneratorData generatorData;
     int selectedLevel;
 
     private void OnEnable()
     {
         generatorData = (GeneratorData)target;
     }
 
     public override void OnInspectorGUI()
     {
         EditorGUILayout.BeginVertical();
         {
             DrawGeneretableDataStatesOnLevels();
         }
         EditorGUILayout.EndVertical();
         EditorUtility.SetDirty(generatorData);
     }
 
     private void DrawGeneretableDataStatesOnLevels()
     {
         EditorGUILayout.BeginHorizontal();
         {
             selectedLevel = EditorGUILayout.IntField("Selected level:", selectedLevel);
             if (selectedLevel < 0)
             {
                 selectedLevel = 0;
             }
             else if (generatorData.generetableDataStates.Count > 0 && selectedLevel > generatorData.generetableDataStates.Count)
             {
                 selectedLevel = generatorData.generetableDataStates.Count;
             }
             else if (generatorData.generetableDataStates == null || generatorData.generetableDataStates.Count == 0)
             {
                 selectedLevel = 0;
             }
 
             if (GUILayout.Button(new GUIContent("Add level", "Add new level")))
             {
                 generatorData.generetableDataStates.Insert(selectedLevel, new GeneratableStates());
                 //generatorData.generetableDataStates.Add(new List<GeneratorData.GeneratableState>());
             }
             if (GUILayout.Button(new GUIContent("Remove level", "Remove selected level")))
             {
                 if (selectedLevel >= generatorData.generetableDataStates.Count)
                 {
                     selectedLevel = generatorData.generetableDataStates.Count - 1;
                 }
                 if (generatorData.generetableDataStates[selectedLevel] != null && generatorData.generetableDataStates.Count != 0)
                 {
                     generatorData.generetableDataStates.RemoveAt(selectedLevel);
                 }
             }
         }
         EditorGUILayout.EndHorizontal();
         EditorGUILayout.TextArea("Count levels:" + generatorData.generetableDataStates.Count);
     }
 }

And other classes:

 [CreateAssetMenu(fileName = "New GeneratorData", menuName = "Generator/GeneratorData", order = 1011)]
 public class GeneratorData : ScriptableObject
 {
     public List<GeneratableStates> generetableDataStates = new List<GeneratableStates>();
 }
 
 
 public class GeneratableStates
 {
     public List<GeneratableState> generatableStatesList = new List<GeneratableState>();
     public GeneratableStates()
     {
         generatableStatesList = new List<GeneratableState>();
     }
 }
 
 public class GeneratableState
 {
     public GeneratableData gd;
     public float perc;
 }
 
 [System.Serializable]
 public class GeneratableData {
 
     public GeneratableData(GameObject prefab, float minScale, float maxScale, Rect boundingRect)
     {
         this.prefab = prefab;
         this.minScale = minScale;
         this.maxScale = maxScale;
         this.boundingRect = boundingRect;
     }
 
     public GameObject prefab;
     public float minScale;
     public float maxScale;
     public Rect boundingRect;
 
     public float GetAverageArea()
     {
         return (boundingRect.height * boundingRect.width) * ((minScale + maxScale) / 2);
     }
 }