You might want to look at Figures 50 - 52 <here>.
Whole notes and above don't work. The limit is 15 grace items.
I think the goal should be to modify playback, not the appearance of View or Print. I'd expect something like this:
!NoteWorthyComposerClip(2.5,Single)
|Note|Dur:8th,Grace,Slur|Pos:2
|Spacer|Width:50
|Note|Dur:4th|Pos:1
|Bar
|Note|Dur:4th,Grace,Slur|Pos:-1
|Note|Dur:4th,Dotted|Pos:-2
|Bar
|Note|Dur:Whole,Grace|Pos:2z^|Visibility:Never
|Rest|Dur:8th,Grace|Visibility:Never
|Rest|Dur:8th,Grace|Visibility:Never
|Note|Dur:8th,Grace,Slur|Pos:2
|Spacer|Width:50
|Note|Dur:4th|Pos:1
|Bar
|Note|Dur:Whole,Grace|Pos:-1z^|Visibility:Never
|Rest|Dur:8th,Grace|Visibility:Never
|Rest|Dur:8th,Grace|Visibility:Never
|Rest|Dur:8th,Grace|Visibility:Never
|Rest|Dur:8th,Grace|Visibility:Never
|Rest|Dur:8th,Grace|Visibility:Never
|Rest|Dur:8th,Grace|Visibility:Never
|Note|Dur:4th,Grace,Slur|Pos:-1
|Note|Dur:4th,Dotted|Pos:-2
!NoteWorthyComposerClip-End
of course you could look at it from the other end. Have the user enter the playback, select it and have a tool turn that into appoggiatura.