private void UpdateScriptObject()
{
var mainAssets = target as Document;
var subAssets = mainAssets.chapters.Where(x => x != null).ToArray();
ScriptableObjUtility.SetSubAssets(subAssets, mainAssets, true);
}
private void OnAddChapter(ReorderableList list)
{
var chapter = ScriptableObject.CreateInstance <Chapter>();
ScriptableObjUtility.AddSubAsset(chapter, target as Document);
prop_chapters.InsertArrayElementAtIndex(prop_chapters.arraySize);
var prop = prop_chapters.GetArrayElementAtIndex(prop_chapters.arraySize - 1);
prop.objectReferenceValue = chapter;
serializedObject.ApplyModifiedProperties();
}