NoteWorthy Composer doesn't support the octave-transposition (8va---) notation directly, but you can fake it and avoid having to use all those hard-to-read ledger lines. Here's how:
For octave-up transposition (e.g. in the treble clef), insert another clef (Insert, Clef) of the same type but with the "octave up" flag set for Octave Shift. Then Insert: Text above the staff: "8va-------^" (use your ASCII creativity). In the Text dialog box Expression Placement, do not put an X in for Preserve Width so the ----- will extend over the notes. Restore the original clef at the end of the sequence.
For octave-down (e.g. bass clef), do similarly, but use the "octave down" flag on the new clef.