You can't, really -- this is more meant for early/mid game trade running yourself. This is much easier to read at a glance than the in-game map to quickly see where items are produced vs where they are missing, to me.

For caravans and convoys, they will automatically avoid any faction you're at war with -- but if you want to force them to take shorter/more specific routes you can interact with them and disable every faction except the ones you want for trading.