Is there anyway of adding cover art metadata support m4a audio files? I know they can support this because I've added cover art to these files before, and they seem to work. I see Cover art metadata is viewable and editable for mp3 and wma already. Going through my audio files I see the same problem exists with flac as with m4a files. Who knows what other audio files could still use cover art support in opus too. Maybe it should check to see if it's there and show it if so for any file that otherwise has music metadata properties.
In terms of displaying the covers in Opus, support is already there for all those formats, I think.
It's read-only, though (at least currently), so it won't appear in the metadata editor like it does for MP3 and WMA.