Currently you have to select both files in the project tree, which is very inconvenient if the files are in separate folders. What I propose is to have a context menu entry "Select <current file> as left side to Compare" and when I have already done that, then another entry should appear "Compare <current file> to <file selected as left side>". That way I can "ctrl-n" go to the first class, then to the second class and easily diff them.