I didn't expect the option to allow carrying items with the cape in the level code and not the library itself since it makes more sense to have it consistent within the whole game and not just singular levels. either way, it's definitively a simple but probably an effective UberASM code.
Some suggestion for next time: Maybe add in the option to set the extra bytes in a later update? It doesn't work with every sprite with more than four extra bytes but these tend to be the exception.
Edit: The option to use the extra bit can also be used, especially with patches which add in a <href="https://www.smwcentral.net/?p=section&a=details&id=22605">extra bit behaviour to vanilla sprites</a>.