I was writting exactly the same thing right now Mike!!
Here's a sample using Glissando.ms version 1.3. Take a look at the (needed for this version) hidden and muted grace note.
!NoteWorthyComposer(2.751)
|AddStaff|Name:"Staff"|Group:"Standard"
|StaffProperties|EndingBar:Section Close|Visible:Y|BoundaryTop:12|BoundaryBottom:12|Lines:5|Color:Default
|StaffProperties|Muted:N|Volume:127|StereoPan:64|Device:0|Channel:1
|StaffInstrument|Trans:0|DynVel:10,30,45,60,75,92,108,127
|Chord|Dur:4th|Pos:3|Opts:Stem=Up|Dur2:4th|Pos2:1
|Bar
|Chord|Dur:Half|Pos:2^|Opts:Stem=Down|Dur2:Half|Pos2:4^
|Chord|Dur:Half|Pos:4|Opts:Stem=Up|Dur2:Half|Pos2:2
|Bar
|Chord|Dur:Half|Pos:4|Opts:Stem=Down|Dur2:Half|Pos2:n6
|User|Glissando.ms|Pos:0.5|Pen:dash|Text:|Scale:100|EndOffsetX:3
|Rest|Dur:4th|Opts:Stem=Up
|Note|Dur:4th,Grace|Pos:-15|Opts:NoLegerLines,Muted|Visibility:Never
|Chord|Dur:4th|Pos:4|Opts:Stem=Down|Dur2:4th|Pos2:6
|Bar
|AddStaff|Name:"Staff-1"|Group:"Standard"
|StaffProperties|EndingBar:Section Close|Visible:Y|BoundaryTop:10|BoundaryBottom:10|Lines:5|Color:Default
|StaffProperties|Muted:N|Volume:127|StereoPan:64|Device:0|Channel:2
|StaffInstrument|Trans:0|DynVel:10,30,45,60,75,92,108,127
|Chord|Dur:4th|Pos:4|Opts:Stem=Up|Dur2:4th|Pos2:2
|Bar
|Chord|Dur:Half|Pos:n4^|Opts:Stem=Down|Dur2:Half|Pos2:6^
|Chord|Dur:Half|Pos:4|Opts:Stem=Down|Dur2:Half|Pos2:6
|Bar
|Chord|Dur:Half|Pos:7|Opts:Stem=Up|Dur2:Half|Pos2:6
|Rest|Dur:4th|Opts:Stem=Down
|Chord|Dur:4th|Pos:7|Opts:Stem=Up|Dur2:4th|Pos2:6
|Bar
!NoteWorthyComposer-End