You can actually delete the duplicates permanently by using this option:
https://www.dropbox.com/s/j57nvenhmeekx ... 2.png?dl=0
when deleting the duplicates within MediaMonkey

No, there is no way to prevent this. If duplicates exist in a scanned location they'll be added.

If you want to keep the duplicates, but not in MediaMonkey you'll need to move them to a location that won't be scanned. Even if you remove a file from MediaMonkey it will be scanned back in next time you scan its location.

Using MM5.0.0.2338, I see how to find and delete duplicates files. But is there a way to prevent importing duplicates in the first place?
This import renames the file with an appended (n). I would like to just reject the import.
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