A small bug. If you hide the articulation the slur is still positioned as though it was visible.
A fix is to move the articulation to the stem, but that's a bit of a pain. You could instead add a second marker (slur) to fix it.
As an aside, it would be useful to have a marker (for slurs or triplet) selected when you enter it (shift@) since you invariably have to reposition it.
I'm not quite following. Can you attach an example of the bad behavior?
Edit: Never mind, I think I see what you mean. You are trying to move the articulation above the slur. When you use the marker to move it, the slur gap is still present. And if you check both the Slur and Articulation box on the marker, then they overlap.
Another Edit: I misread, you are trying to hide the articulation, not move it. So putting it on the stem side is probably an easier fix, since you are hiding it anyway. But I see your point: if you are making the articulation invisible, it would make sense to collapse the slur position as though it were not there.
It's still nice to include an example when you are reporting a bug, so people can see what the anomaly looks like.
Then use two markers:
!NoteWorthyComposer(2.751)
|AddStaff|Name:"Staff"
|StaffProperties|EndingBar:Open (hidden)
|Marker|Pos:5
|Marker|Pos:6.5|Target:Articulation
|Note|Dur:4th,Slur,Accent|Pos:3
|Note|Dur:4th|Pos:4
!NoteWorthyComposer-End
I had thought of using the marker to hide the articulation and to position the slur. This does indeed work, but unfortunately the slur is hidden too!
This also works:
!NoteWorthyComposer(2.751)
|AddStaff|Name:"Staff"
|StaffProperties|EndingBar:Open (hidden)
|Marker|Pos:6.5|Target:Articulation
|Note|Dur:4th,Slur,Accent|Pos:3|Opts:ArticulationsOnStem
|Note|Dur:4th|Pos:4
!NoteWorthyComposer-End
Check 'Use stem for articulations.' This auto-positions the slur and the articulation Marker puts the accent back on the head.