When a page has a lot of resources, you have to scroll a lot to switch between one resource and a graph. The design to resolve that could be related to "Inspector's timeline should show a tooltip with duration for each resource " (https://bugs.webkit.org/show_bug.cgi?id=18035)
How would this be related to bug 18035?
Maybe the graphs could be shown all the time. When you scroll the resources, the graph section is not scrolled. This way, when you select a resource, the graph could show the duration for this resource with another color.
Tht would take up a lot of room, and in docked mode that is room we don't have.