How do I enter a sforzando (or a similar character) so it appears directly under the note or notes? Thanks.
If you mean what I think you mean then UNCHECK Preserve Width when entering the mark.
How does one put in flow directions such as D.C. al Fine directly under notes. Why do some things have preserve width boxes and others don't?
If you don't care about playback but about how the printed page looks you can add text above or below the staff for everything but the coda and segno symbols. Staff Italic I think is the font used for flow direction.
You can insert any native nwc symbols (incl. segno and coda symbols) as text by assigning one of the user fonts to nwcv15.ttf.