In the Notation Window, clicking on the "Opt." button brings up the Notation Windows Options dialog.

In that window you can set the "Clefs split at:" for where notes placed on the staves, are to be located on the treble or bass clef.

The default split point is "C4". Anyone unfamiliar with this numbering system, wouldn't know whether the next note "up" was C#4 or C#5. Similarly, is the next lower note "B4" or "B3"?

If the entry box here had "spin arrows" (like the ones to set Tempo), you could set the clef split point "higher" or "lower", simply by clicking the up or down arrow, without having to know anything about what "C4" meant.

Thanks!
LLOYD S