You can do it in the vanilla game. Just go to your Quickslot options under Appearance and quickslot the Hide Your Helm collectible. Then You can use your Quickslot bar as the toggle,
Before ZOS moved the hide helmet from settings to the outfit system, there was an addon that allowed most (all) vanilla ON/OFF toggles, including the Helmet toggle to be hotkeyed. It's called Quick Settings, and is a very nice addon. Although it can no longer be used for the Hide Helmet setting, there are still plenty of other toggles that you may find use for this addon...