Hyphens, En Dashes, Em Dashes

Q. Does CMOS have an official position on hyphenating “the then” when used to indicate something or someone’s former status?

A. Because then as an adjective is subject to being misread (unlike former), CMOS advises adding a hyphen or, next to an open compound (as below), an en dash: 

• the current secretary of state
• the previous secretary of state
• the then–secretary of state

See CMOS 7.96, section 3, under “then.”

[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]