I noticed something very confusing about HD500 Edit that I couldn't find was written about anyplace. Before I figured this out, it was extremely maddening, but after figuring out the details, I find it useful.
In the MIDI Assign pane of the Controllers tab, you can mouse-over and use the scroll wheel to adjust knobs or fields, OR click a knob or field and press the Up or Down arrow keys. This behavior changes depending on whether you click/mouseover the Footswitch graphical KNOB, or click/mouseover the TEXT FIELD next to the knob.
--> If you use the knob itself, changing the value just moves between the settings of various footswitches (you'll see the other options bouncing around).
--> If you use the text field, changing the value *copies* the currently displayed settings to the other footswitches you scroll through.
I hope this is useful for everybody.