Unfortunately, my IDE does not support Drag&Drop FROM my app. I'm totally annoyed about that, too.
BUT you can add "userdefined actions" in the settings dialog.
MP3Tag
To call Mp3Tag on windows, this action would do the task:
C:\Program Files\Mp3tag\mp3tag.exe "$filename"
Modify Tags
To e.g. set the COMMENT-Tag, you could set this action:
tag:set comment Real bitrate: $realbitrate kbps