Serializating a base class array to a prefab

I have been dealing with this issue for the whole week and I am kind of stuck and out of ideas.

I am working in a quick item editor. Each item may have one or more properties. These properties have all a common parent since they have common properties. Each child may also have particular properties.

I want to use the editor to show the properties array, edit it, and when finished, save the created gameobject to a prefab.

I almost have it working but I am facing a problem:

• If I make MyBaseClass not to inherit from ScriptableObject (see comments on code below), everything works almost like a charm, but the child objects are casted to the parent class and they will remain like that forever. This problem was already stated here and was supposed to be solved with the next option, which is:

• If I make MyBaseClass to inherit from ScriptableObject everything works fine before prefab creation, but then after creating the prefab, the array seems to be in a corrupted state. It seems that the CustomEditor is no longer correctly executed for that prefab.

This is my code, simplified for a better understanding. Just create each script separately (it should run as it is) and drag the SerializeMe.cs to a gameobject to reproduce the scenery. Remember to store SerializeMeInspector.cs into the Editor folder.

SerializeMe.cs

 using System;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEditor;
 
 [Serializable]
 public class SerializeMe : MonoBehaviour
 {
     [SerializeField]
     public List<MyBaseClass> m_Instances;
 
     public void OnEnable ()
     {
         if (m_Instances == null)
             m_Instances = new List<MyBaseClass>();
 
         hideFlags = HideFlags.HideAndDontSave;
     }
 }

MyBaseClass.cs

 using UnityEngine;
 using System;
 
 [Serializable]
 public class MyBaseClass : ScriptableObject
 //public class MyBaseClass
 {
     [SerializeField]
     public int m_IntField;
     
     public void OnEnable()
     {
         hideFlags = HideFlags.HideAndDontSave;
     }
 }
 

ChildClass.cs

 using UnityEngine;
 using System;
 
 [Serializable]
 public class ChildClass : MyBaseClass
 {
     [SerializeField]
     public float m_FloatField;
 }

SerializeMeInspector.cs (stored in the Editor folder)

 using UnityEngine;
 using System.Collections.Generic;
 using System;
 
 [CustomEditor(typeof(SerializeMe))]
 public class SerializeMeInspector : Editor
 {
     SerializedProperty SP_m_Instances;
     
     public void OnEnable()
     {
         SP_m_Instances = serializedObject.FindProperty ("m_Instances");
     }
     
     public override void OnInspectorGUI() 
     {
         serializedObject.Update ();
         
         if (GUILayout.Button ("Add Base"))
         {
             //(target as SerializeMe).m_Instances.Add(new MyBaseClass());
             (target as SerializeMe).m_Instances.Add(
                 (MyBaseClass) ScriptableObject.CreateInstance("MyBaseClass"));
         }
         
         if (GUILayout.Button ("Add Child"))
         {
             //(target as SerializeMe).m_Instances.Add(new ChildClass());
             (target as SerializeMe).m_Instances.Add(
                 (MyBaseClass) ScriptableObject.CreateInstance("ChildClass"));
         }
         
         for (int i = 0; i < SP_m_Instances.arraySize; i++)
         {    
             EditorGUILayout.Foldout(false,"Element #"+i);
             
             MyBaseClass parent = (target as SerializeMe).m_Instances[i];
             
             // Base common display
             parent.m_IntField = EditorGUILayout.IntField(
                 "Base prop", parent.m_IntField);
             
             // Child display if casting is a success
             ChildClass child;
             try 
             {    
                 child = (ChildClass) parent;
             }
             catch (InvalidCastException)
             {
                 child = null;
             }
             
             if (child != null)
             {
                 child.m_FloatField = EditorGUILayout.FloatField(
                     "Child prop", child.m_FloatField);
             }
             
         }
         
         serializedObject.ApplyModifiedProperties ();
     }
 }

I'd really appreciate any ideas or help with this.

Thank you very much in advance.

EDITED: Some code added as suggested by Bunny83, but still not working