private void DrawPrefabs(TARGET tgt)
        {
            var rectA = Reserve();
            var rectB = rectA; rectB.xMin += EditorGUIUtility.labelWidth;

            EditorGUI.LabelField(rectA, "Prefabs", EditorStyles.boldLabel);
            var newPrefab = EditorGUI.ObjectField(rectB, "", default(Object), typeof(Object), false);

            if (newPrefab != null)
            {
                Undo.RecordObject(tgt, "Add Source");

                tgt.AddPrefab(newPrefab);

                DirtyAndUpdate();
            }

            BeginIndent();
            for (var i = 0; i < tgt.Prefabs.Count; i++)
            {
                DrawPrefabs(tgt, i);
            }
            EndIndent();
        }