Methyltransferase required for the conversion of demethylmenaquinol (DMKH2) to menaquinol (MKH2). a 2-demethylmenaquinol + S-adenosyl-L-methionine = a menaquinol + H(+) + S-adenosyl-L-homocysteine Quinol/quinone metabolism; menaquinone biosynthesis; menaquinol from 1,4-dihydroxy-2-naphthoate: step 2/2. Belongs to the class I-like SAM-binding methyltransferase superfamily. MenG/UbiE family.