For the purposes of this question, "Trump's cabinet" is defined as any of the 24 members of Cabinet and Cabinet-level officials serving at the pleasure of the presient. 

Only members who have assumed office will count

, meaning a failed confirmation won't count. This question resolves YES if Elon Musk is out of his Government Efficiency effort role (and only if he doesn't leave that role to take some other position in the administration, such as an "advisor to the president"). If Elon leaves his Gov. Efficiency role for a cabinet position before anyone else assumes that role, this question resolves N/A. 