I was looking to do the same. Currently with the single line selected, the option to customize the display is greyed out and is fixed at <Artist> - <Title> and only when multiple lines are enabled can these by changed. I'd like to have a single line only for a more compact bar, but choose the fields to show up. i.e. <Disc#>-<Track>. <Title> [<Year>]. Any chance this is planned for a future update?