Here's an example of why the breve (double whole note) is needed:
!NoteWorthyComposerClip(2.0,Single)
|Clef|Type:Bass
|Key|Signature:Bb,Eb,Ab
|TimeSig|Signature:4/2
|Tempo|Base:Half|Tempo:96|Pos:9
|Note|Dur:4th,Slur|Pos:4
|Note|Dur:4th|Pos:3
|Note|Dur:Whole|Pos:4
|Note|Dur:4th|Pos:6
|Note|Dur:4th|Pos:5
|Bar
|Text|Text:"z"|Font:User1|Pos:7
|Note|Dur:Whole,Slur|Pos:4^|Visibility:Never
|Note|Dur:Whole,Slur|Pos:4^|Visibility:Never
|Bar|Visibility:Never
|Text|Text:"z"|Font:User1|Pos:7
|Note|Dur:Whole,Slur|Pos:4^|Visibility:Never
|Note|Dur:Whole,Slur|Pos:4^|Visibility:Never
|Bar
|Note|Dur:4th,Slur|Pos:4
|Note|Dur:4th,Slur|Pos:3
|Note|Dur:4th,Slur|Pos:2
|Note|Dur:4th,Slur|Pos:3
|Note|Dur:Whole,Slur|Pos:4^
|Bar
|Note|Dur:4th,Slur|Pos:4
|Note|Dur:4th,Slur|Pos:5
|Note|Dur:4th,Slur|Pos:6
|Note|Dur:4th,Slur|Pos:5
|Note|Dur:Whole,Slur|Pos:4^
|Bar
|Note|Dur:4th,Slur|Pos:4
|Note|Dur:4th,Slur|Pos:3
|Note|Dur:Half,Slur|Pos:4^
|Note|Dur:4th,Slur|Pos:4
|Note|Dur:4th,Slur|Pos:3
|Note|Dur:Half|Pos:4
!NoteWorthyComposerClip-End
(The breves are a text expression using MusiSync, Bold [11].)
The ties and slurs are not visible when the semi breve (whole note) is set to Never under Notation Properties\Visibility.
If a functional breve cannot be added, it would be helpful to have the option where the slurs and ties would remain visible under Notation Properties\Visibility when the note is set to Never, or the possibility of adding ties and slurs to the Text Expressions.