Special endings only apply to NWC Master Repeats, so you could use this kind of thing (along with changing the opening repeat to a Master Repeat):
!NoteWorthyComposerClip(2.0,Single)
|Ending|Endings:1
|Dynamic|Style:mp|Pos:-8|Wide:Y
|Bar|Style:MasterRepeatClose
|Ending|Endings:2
|Dynamic|Style:pp|Pos:-8|Wide:Y
|Bar|Style:MasterRepeatClose
|Flow|Style:Fine|Pos:6|Wide:Y
!NoteWorthyComposerClip-End
However, I would generally recommend that a fade be done using an Expression change with a Multi-point Controller. You could replace each of your local repeat open bars with this selection:
!NoteWorthyComposerClip(2.0,Single)
|MPC|Controller:exp|Style:Linear Sweep|TimeRes:Whole|SweepRes:1|Pt1:0,127|Pt2:12,0|Pos:-7|Wide:Y|Justify:Right|Placement:BestFitForward
|Text|Text:"Fade Out"|Font:StaffItalic|Pos:-10
|Bar|Style:LocalRepeatOpen
!NoteWorthyComposerClip-End
If you use this second solution, make sure to remove the extraneous special endings, as well as the dynamics, as they are not needed.