Inspector - editing array of polymorphic objects?

So I have a ScriptableObject with an array of polymorphic objects like this:

 [System.Serializable]
 public class CMyObject : ScriptableObject 
 {
     public List<CElementBase> _Elements = new List<CElementBase>();
 }
 
 [System.Serializable]
 public class CElementBase
 {
     public string _Name;
 }
 [System.Serializable]
 public class CElementInt : CElementBase
 {
     public int _SomeInt;
 }
 [System.Serializable]
 public class CElementString : CElementBase
 {
     public string _SomeString;
 }

Is there a good way to use the inspector to add and edit derived-class element to the array?

I was able to add the support for adding derived classes using CustomEditor for MyObject and

 public override void OnInspectorGUI() 
 {
     DrawDefaultInspector ();
     CMyObject myTarget = (CMyObject) target;
 
     if(GUILayout.Button("Add Int"))
     {
         myTarget._Elements.Add ( new CElementInt() );
     }
     if(GUILayout.Button("Add String"))
     {
         myTarget._Elements.Add ( new CElementString() );
     }

But even so, the elements that show up in the array only allow me to edit the base class properties (_Name), not the derived class ones (_SomeInt or _SomeString).

Is there a way to have Unity let me edit the actual derived class, or do I need to manually create edit fields for each property based on the type? Please advise!