Now that I know what I'm looking for, I can add a couple comments...
(I believe) The description of this functionality is in the 1.8 manual
tutorial on Page 15, under 'Voice Triggering'. It states "Voices can
be turned on and off independently of the play button. ", but then
immediately and subsequently refers to that as triggering.
Semantics, my excuse to not embrace that term for turning something
OFF, but the information IS here.
If there is another detailing of the function in the manual, I have
not found it.
There are minor proof-reading items in this tutorial section. There
are a couple numbered sections below the quote I gave above. It seems
there was a step removed somewhere, and the numbering doesn't match
the text now.
The text is:
You will notice it is possible to turn off voice
groups and then turn them back on using step
48.
When it really means to refer to:
47. Option-click (Mac) or Alt-click
(Windows) on a Voice Group Triangle.
There is another a little further on...
The text is:
Notice that the voice group you selected in
step 49 is not active when Nodal is playing.
When it really means to refer to:
48. Select a starting triangle and in the
Voice Group Inspector, enter a MIDI
pitch value (C3 for example) in the
MIDI Pitch List field as shown above.
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I leave the original request there, unless someone has something to
add...
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NEW - In addition (now that I know to use this):
It would be nice if the route enable/disable I configured, was
persistent across use of the play/pause control.
I have mixed feelings; but could understand if, pressing the 'rewind'
button - returned all voice groups to their defined state. That gives
a quick way to revert, while not forcing me to re-defined what's
playing, every time I stop playing to make node edits.