Thank you Mr Klorox, for the suggestions. At this time I cannot edit the Whitelist directly -- for the reason I gave above (this GUI interface things must be fixed!) -- to allow entry from another computer on the LAN -- but with a browser on the same PC, then yes! the text boxes are editable.
Brilliant!
Okay, so here I put in some scheduling and some .sts entries, as shown here:

.
And now we wait to see if the Scheduler does its job (if I did my part correctly) . . . <taps foot impatiently> . . . three minutes now to 1655 and it is Tuesday . . . and . . . no, I am sorry to say that Stereotool did not switch to the different preset as I hoped. The (partially hidden, possibly a browser issue) view of the active Preset here

shows the Preset that was running before the switch I hoped for.
It appears that the Scheduler is not paying attention to me. I may be doing something wrong?
Thank you for your help!