'all tracks could tell you in what playlist the original song is located & it's copies in others

It doesn't work that way - there's no concept of 'home' playlist for a song. There's no directory structure on the data partition(s) of the empegs disk(s), all tunes are just tossed into one big pile. Then the file name/number (FID) is entered (or not, then you have a tune with refs=0) into one or more playlist. All playlist are, in this way, equal -- no playlist is given any special treatment just because it was there you initially dropped the file in emplode.

One way of spotting duplicates is to goto All Titles, sort on Title, add the FID column (under the View -> Columns...) Now, any two lines with the same Title and Artist are suspect (but not automatically duplicates, as it could be different versions...)

Another way is to export the DB to CSV, import into a database and make a join query on the table with itself, somethig like this:
SELECT Empeg.Artist, Empeg.Title, Empeg.FID
FROM Empeg, Empeg AS Empeg_1
WHERE Empeg.Artist = Empeg_1.Artist
AND Empeg.Title = Empeg_1.Title
AND Empeg.FID <> Empeg_1.FID;

Anything returned has identical Title and Artist but different FIDs - suspected duplicates. Add more fields (like duration, length etc) to easier/more certain spot duplicates, both to display and in the query itself...

/Michael