A grace note is a note usually displayed as a smaller sized note which does not have duration of its own. The duration of gracings is borrowed from the next normal-sized note (to which it usually connected with a slur). Grace notes are inserted with the grace note menu
Grace notes are by default always shown with stick pointing up. Of course you can specify stem-direction manually. Hitherto you'll use menu-others.
It is possible to cluster two or more grace-notes to form double or triple gracing.
Although grace notes are of the same size as cue notes, they serve different goals, and are interpreted very differently.