Took many days to reach this level!
Comparing to the previous update, it seems like I just added a note to the scene, but it is actually much more advanced.
I managed to make sure every level can be instantiated based on a JSON file, and when the level is initialized, each note is created based on this JSON config, game objects are created with the correct scripts configuration and sprites on activation, active duration, etc.
This is such advanced work for me, I'm really proud of it!