The robot plugin's trend graph is a great way to show test status over time.

However, over time the number of tests in our projects overall grow, and we keep on top of the number of failures, so the number of tests is fairly high now (around 9000) and the number of failures at any point is quite low (between 5 to 30), so the trend graph doesn't give us much indication of the number of failures compared to previous points in time (we just see a green graph). It would help us a lot to be able to see a trend graph which was filtered for just failed tests.