I wonder if someone can help me out of this tight corner.

By putting together seven files I'm trying to create a single composite
file. All the seven are written in a similar style. No endnotes, but only
footnotes.

1) In one case, when I copy the file and add to the composite file, all
footnotes get lost.
2) In another case, footnotes are converted to endnotes.
3) In some other files footnotes have been incorporated into the main text
in a smaller font as in the original.
4) In some files added to the composite file, NWP doesn't allow me to add
footnotes or endnotes.

Part of the explanation may be that some of the original files have been
converted from the Word format and reconverted to the Nisus format. The
first file was written more than a quarter of a century ago!
Best wishes,
Takamitsu MURAOKA