Who copied the additional proverbs of Solomon in Proverbs 25?

Answer: The men of Hezekiah

"These are additional proverbs of Solomon, which were copied by the men of Hezekiah king of Judah."

“These are additional proverbs of Solomon, which were copied by the men of Hezekiah king of Judah:”— Proverbs 25:1 (BSB)