The graph at the bottom shows the amount of time spent on the selected item from the total logged time by day.
It is already possible to export the data to JSON. This has been added to allow you to use this data in your personal sites or recovery on a new PC. But I did not think about combining the data :(
I should have some free time next month, I'll try to come up with something to close this problem and refresh the application as a whole. I think it should be interesting :)