As of Bovy version 1.10, released April 10, you can now see some simple graphs of test day information.
There are a couple ways to do this. You can just say or type "Graph" then the field you want to graph - for example
Or you can click the new graph button on the Ask Bovy page and you'll see a pick list of the test day items you can graph :
So it's pretty easy.
Understand that Bovy only has a "snapshot" of your latest test day, it doesn't have all the test days for a cow. So the graph shows all the cows, with the value (Milk, Percent Fat, MUN etc) plotted against the days in milk. So while this feature might not have a great amount of management value, it is interesting to try it.