Arcade Extension Development Help

Hello! I am currently coding an extension for arcade, that allows users to play piano chords without having to use the piano blocks or the timer blocks. I want the block to have three drop down menus. One to choose the chords, one to choose the pitch (high, middle, or low), and the last one to choose how long will it play for. Does anyone know how I can do this?

so do you want to learn how to make an extension?
if yes then i can teach you