The file acciacc.nwc (http://www.noteworthysoftware.com/composer/files/acciacc.nwc) (1K) shows an example of how to notate an acciaccatura (place in muted print group) and two ways to notate it (place in play group) - played on the beat or just before the beat.
Editor's Note: For more details on creating a print group and play group, see the user tip https://forum.noteworthycomposer.com/?topic=2277. D. G. Catt has created a font (http://www.noteworthysoftware.com/composer/files/nworn.zip) that has a small slash and slur to use in place of the full size slash and slur (as the above example uses).