Not satisfied with the way Europa Universalis IV only presents its trade data in numerical form, I made this tool to load EU4 saves, read their trade data and produce a map that shows the values of all trade nodes and trade routes visually, by drawing circles and arrows of sizes and widths corresponding to their magnitudes.
If you're not interested in the code and you are on Windows, you'll just want to download this zip.
For more information and support, check out the thread on Trade Visualizer on Paradoxplaza (thread is only visible if you have an account and registered EU4).
Note that the name Europa Universalis IV, its world map, trade network and the merchant icon are intellectual property of Paradox Development Studio or derived from it, and the included GPL3 license does not extend to these resources. They are only included in this piece of software under the assumption of fair use, and I do not claim any rights or ownership.