An unused Trade Workshop building can be found in the game's data. It was originally planned to function as a building where to player could assing villagers to produce "Luxury Good", which could be sold for gold. Though scrapped, remnants of their existence can still be found in the game's scenario editor, with its icon resembling the Market economic building. The building can also be seen in several scenarios, too.
It's possible to extract campaigns from the game itself and edit them like Custom Scenarios.