If you knew it long ago, please don't laugh at my stupidity.

You are very clearly
not stupid.
I suspect that most of us don't use Sforzando. I was unaware of the keyboard on it. Good find.
Something that your image shows is that it is displaying a particular "voicing" of an ordinary C major chord and I have often wondered if the different possible voicings may be one of the things that sometimes make it hard for you to understand the chords.
I think sforzando as supplied with BiaB has only a few instruments, but you can download other instrument libraries for it. There are a number of good sound libraries around that Sforzando can import. Try
Compifont,
JJazzLab-SoundFont or
Timbres of Heaven. Sforzand have some on their website, both free and paid.