I think you can view trade agreements from the [c]iv screen. I also think the suggestion is a good one, though with the civilizations mixing the way they do now you might find the demand for narrow/large crap back home is higher than you'd expect.
You were right about the trade agreements being visible on the civ screen, thanks for the info.

When the Caravan Arc rolls around - or at least the tasks that are currently grouped under that headline - I imagine trading will become a whole lot more complex in all kinds of ways, presumably the incoming traders will have more specific needs and wants in mind. If nothing else this would be needed to make it consistent with any caravans the player sends out.

Not that I know if anything like that is really planned, but I sure hope so. It'd be awesome.
Pack a lot of masterwork rock items in a cart, designate a bunch of dwarves as merchants and guards and send 'em off to the elves to trade for wood or cloth, then wait a bunch of months, hoping for the best, until they either return (hopefully with a sensible profit) or news arrive that their were ambushed or whatever. It'd be a big gamble - sending lots of dwarves out into the big bad world without you to protect them - but potentially
very profitable. Kinda like financing a merchant ship bound for India back in the 15th century.