Batch Edit Album Art from Progressive to Baseline Support?

I have a ~10,000 library of album art-embedded MP3s, but unfortunately my music player cannot detect the album art because it is in progressive format. All other metadata are properly detected.

Does MP3Tag have a batch edit for changing album art from progressive to baseline type?

No.
you would have to export the embedded pictures to the file system,
convert them with a suitable program.
re-import them into the audio files

The picture files can be exported and imported by MP3tag with an action (sort of batch process).

Thats pretty unfortunate in my case with ~10,000 songs.

Regarding the export and re-import steps, could you share the way how to do it using action?

See the FAQs/Howtos on how to create an action:


and
http://help.mp3tag.de/options_format.html#exportcover

Use an action of the type "Export cover to file" to export.
Enter a useful format string like
Format String: %album%_%title%_%cover_type%
Execute the action.

Do the conversion.
See the help on the next action type:
http://help.mp3tag.de/options_format.html#importcover

Create an action of the type "Import cover from file"
Format string: %album%_%title%_%cover_type%.jpg
Tick "Remove existing covers"
Execute the action.
This should be it.

Aright Ill give this a try later today, thanks a lot!