In the comparasion UI, the "waterfall opacity" should be floating

[jpvincent]

Feature Request Summary

I use a lot the opacity feature to compare 2 runs

Here I can compare what's different in the first requests of the page.

My problem comes when comparing HTTP waterfalls that are more than 50 lines long, and that's now the majority of websites. I want to use the opacity

Here, if If I want to spot a difference happening late, I have to scroll up, change the opacity, scroll down all the time. I need to have the slider at hand anywhere in the page.
That could be in a layer floating on the top of the waterfall, or in a component in the right or left side of the comparison.