As per the title, is there any way to turn off the ‘New’ banner that appears top left on any new Cd’s added to the library.
No, but the banner is removed when an album is played or after a week.
This annoys me too, but you can click play, then move the cursor to the end of the track while still in playback - the track finishes, the next one starts, and the NEW banner disappears. Seems you must have heard two tracks for it to no longer be “new”.
And of course, for those that add many new items to our collections every week “New” it is a useful reminder.