knick-knacker, n. — Green’s Dictionary of Slang

knick-knacker n.

also knicknack

[SE knick-knack, one whose mind is limited by their obsession with trivia]

(US) a fussy, officious person.

1967		Reynolds & McClure Freewheelin Frank 136: Many of us [...] have no driver’s license, because of the knickknackers in white shirts in the DMV, Department of Motor Vehicles.
1971		Black Scholar Sept. 35: I thought you were some kind of knicknack [HDAS].