Here are related feature requests…
Bulk Delete of Red Tracks in Engine DJ App - has 16 votes. There are some links to old feature requests there too. Plus, @djliquidice offers a Bash shell for listing the missing files referenced in Engine Library m.db.
Enable Sort by DIRECTORY Column - has 8 votes. (Submitted by @Mixlive in response to @some_po 's thread Sort for Missing Tracks to Delete.)