(If gold were as cheap as copper, what would we do with it that we don’t do already?)
Are you asking what uses would humanity intensify and employ even more gold for than we already do now, or what entirely new uses (which are currently uneconomical or have not been discovered) we would employ gold for? Because at least for the former, there’s a variety of uses for gold: https://en.wikipedia.org/wiki/Gold#Medicine (and scroll down for further uses).
Are you asking what uses would humanity intensify and employ even more gold for than we already do now, or what entirely new uses (which are currently uneconomical or have not been discovered) we would employ gold for? Because at least for the former, there’s a variety of uses for gold: https://en.wikipedia.org/wiki/Gold#Medicine (and scroll down for further uses).
Both are good ways to answer.