· What about editing/renaming multiple copies of the same song?
Assuming that you didn't deliberately upload the song twice, then any edits you make to the song in playlist A will automatically appear in its copy in playlist B. They are both links to the same database entry.
This goes for playlists, too. When you move and copy playlists in Emplode, you're working with the database link to the playlist. So if you make a copy of a playlist, then edit one copy, the changes automatically appear in the other copy. (If you don't want this to happen, then create a new playlist from scratch instead of making a copy of it.)
By the way, beginning with Emplode version 2.0 and later, you can group-select songs or playlists and edit their properties as a group. This is helpful when re-tagging entire albums.