Welcome 
This has been discussed a few times over the years [1] [2] [3], but currently, file de-duplication falls outside the scope of Picard’s abilities.
Not sure what system you’re running on, but there’s likely an application available that’s suitable for de-duplication. On Linux, Windows, macOS and FreeBSD, there’s the excellent and free Czkawa, which can scan for files with similar tags, or by audio content using something similar to AcoustID.
