Preventing bar lines across staffs

How can I prevent bar lines extending across the staffs in a piano part (to leave the space clear for a lyric, as is common in hymn books)? Presumably, I have to ungroup the left- and right-hand parts, but I can’t work out how to do that.

You could manually un-attach them using the custom barline tool in engrave mode. Or choose Choir reduction instrument.

Got it! Thanks.