Another thing I'd like to see is some indicator (maybe in the sidebar, as a fixed thing that scrolls along) that shows, to which trait do the methods shown belong. If there are tons of traits and they have tons of methods that each have many paragraphs of text and examples (the String API is an obvious example), you easily lost sense of the big picture.
I used to cmd-F inside the page to try and find relevant functions, but after finding what I was searching for, I had to scroll a bunch to learn what trait I had to import to use the methods.
I don't have any concrete design proposal, just stating the problem. But maybe it would help if the trait subheader simply scrolled along or something...?