Works very well, thank you! Is there an easy way to apply this in bulk to multiple different audiobooks? Selecting multiple books applies the same metadata to all, very helpful for split audiobooks. But I have a large library to go through, all of them single file m4b, so if instead of applying the same metadata to all, it could open each file in sequence, that’d be very convenient.
It's only available on a per-album/per-audiobook basis. It's not possible to bulk update all your audiobooks at once with Mp3tag.