um, not sure if i understand you correctly. you will probably need to go through each track and edit info individually, i don't think there's a bulk edit option on something like comments.
if u mean you cant see comments category right click where 'artist' and 'genre' are, that should give you a drop down menu which u can tick boxes to select/deselect whatever info you wish to be displayed along the top.
also if you mean selecting multiple tracks for adding to playlist just hold shift while selecting..