Yes, HIGHLIGHTED is a Scrabble word!

Letter values in Scrabble US: H 4, I 1, G 2, H 4, L 1, I 1, G 2, H 4, T 1, E 1, D 2.

Is it a valid word?

HIGHLIGHTED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

move into the foreground to make more visible or prominent
apply a highlighter to one's cheeks or eyebrows in order to make them more prominent

Also: play up.