It appears to correctly save new input values, and to correctly display new and existing input values. It may be a while before I can do a listening test; speaking of which, I notice a Reverb on the toolbar--does this incorporate the Soundfont send values? If so, the listening test would go a lot faster.
(I answered my own question: the reverb does indeed use the send values. Very nice! But I can't turn it on or off reliably--I have to change presets to get it to respond to the checkbox. And the "Amount" seems to be set by the "send" levels and cannot be set manually, correct?