This has been done before but I applied it differently to make it look like a custom-made dropdown. It's really unimpressive once you figure out how it works. This is also a good time to ask: why hasn't Scratch Team added this yet? Just have an option for "create a new dropdown" and then once you click it you can add items to a list that creates the dropdown. It's definitely possible, though I'll admit it took some time for me to get this to work so I don't know if ST would be up for it.
i didnt make the block