I lost trace of the open issues with ties and slurs, so bear for me if this is already known.
In this snippet
!NoteWorthyComposerClip(2.0,Single)
|Chord|Dur:4th,Dotted|Pos:n1^|Opts:Stem=Up,Tie=Upward|Dur2:4th,Dotted|Pos2:b0
|Chord|Dur:4th|Pos:1|Opts:Stem=Up,Tie=Upward|Dur2:4th|Pos2:-1
|Bar
|Chord|Dur:4th,Dotted|Pos:n0^|Opts:Stem=Up,Tie=Upward|Dur2:4th,Dotted|Pos2:-1
|Chord|Dur:4th|Pos:0|Opts:Stem=Up|Dur2:4th|Pos2:-2
|Bar
!NoteWorthyComposerClip-End
the tie is fine until the lower note is added, then, as you can see, the tie "slips down" looking like a slur for the lower note.