Hyphens, En Dashes, Em Dashes

Q. Dear Chicago experts, can you please help resolve this hyphenation issue? Should it be “worm composting expert” or “worm-composting expert”? Should it be “worm composting master” or “worm-composting master”? Thank you very much.

A. Use a hyphen; it makes it clear that the expert or master is not a worm.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]