I’m looking for a way to add/toggle item properties for products already inside of a cart drawer. Prior dev has cart.js installed but not sure exactly how/if to leverage that. They mostly used the “data” method but don’t see a way to use that for updates. Looking for any direction here 
As far as I know there is no way to add/toggle item properties for products in the cart drawer.
You can just add properties at product page and show it in cart drawer. Refer https://www.youtube.com/watch?v=5b_5tFOzYuU
Hope it helps!