Saving nested data with AssetDatabase.CreateAsset

Hi.

I got a nested structure of ScriptableObjects which I want to save and load from an .asset file.

So, I basically do this:

 var bla = ScriptableObject.CreateInstance<Bla>();
 bla.TheList.Add(ScriptableObject.CreateInstance<Bla2>());
 bla.TheList.Add(ScriptableObject.CreateInstance<Bla2>());
 
 var fileName = EditorUtility.SaveFilePanelInProject("Save effect", "1.asset", "asset", "");
 AssetDatabase.CreateAsset(bla, fileName);

Where Bla and Bla2 are the following simple classes:

 [Serializable]
 class Bla : ScriptableObject
 {
     public float A = 1;
 
     [SerializeField]
     public List<Bla2> TheList = new List<Bla2>();
 }
 
 [Serializable]
 class Bla2 : ScriptableObject
 {
     public float B = 3;
 }

But the problem is that the list of Bla2 doesn't get serialized automatically. Trying to find a workaround I did the following:

 foreach (var bla2 in bla.TheList)
 {
     AssetDatabase.AddObjectToAsset(bla2, fileName);
 }

And now data from the list gets serialized. But this was just an example. In real life I got lots of nested stuff inside the objects of the list which must be serialized too. So I'll have to loop over all of them recursively using something like a visitor pattern or whatever.

What am I doing wrong? Is there a simpler way to do this?

Thanks.