When studying often times I like to see more then one book or chapter at the same time, I don't use the commentary window that much at all would be nice if I could add another Bible window
What I typically do is clone the Bible panel when I am studying a chapter. That lets you keep a panel for the chapter under study but still easily move around in the rest of the program (including the Bible panel)... not exactly the same thing but if you're not familiar with it, it may be what you want...