How to initialize array[][] via SerializedProperty?

I need to create an Array of MyType from EditorScript and initialize it. But I have problems with serialization. MyType is serializable.
In Monobehaviours script this operation very simple

var obj = new MyType[rows];
for (int i = 0; i < rows; i++)
obj = new MyType[columns];
But how can I do the same thing in EditorScript when I use SerializedProperty?

Unity’s serialization doesn’t support a multi-dimensional array (array). See:
towards the bottom “Note: Unity doesn’t support serialization of a List of Lists, nor an Array of Arrays.”

Since the serialization doesn’t support it I’d doubt that their serialization classes would support it.

One possible workaround would be to flatten your array, instead of an array[y] you’d have array[x*y]