Thanks for the tip FredWBauer,
Here was I did and what happened:
I modified by config.cfg file to include these lines:
trigger mode: repeat
trigger start threshold dB: -35
trigger start threshold linear: 5 (actually I'm not sure about this integer)
trigger stop threshold dB: -65
trigger stop threshold linear: 10 (actually I'm not sure about this integer)
When I attempted to record it seemed to work correctly.
I raised and lowered the gain and ended up with a few separate files.
When I re-examined the config.cfg file it looked like this:
# .cfg file created by rockbox r23746M-091125 - http://www.rockbox.org
volume: -26
rec path: /recordings
rec mic gain: 8
trigger stop threshold dB: -65
trigger mode: repeat
Returning to Rockbox and entereing recording I attempted to modify the trigger settings and the start/stop gain thresholds would stick at -84 (or OFF) as previously described.
Examining the config.cfg file after having attempted to modify the trigger settings it still looked like this:
# .cfg file created by rockbox r23746M-091125 - http://www.rockbox.org
volume: -26
rec path: /recordings
rec mic gain: 8
trigger stop threshold dB: -65
trigger mode: repeat
Exactly the same! Something is not accepting changes somewhere in the trigger code.
I rarely use the trigger function, but when it's needed it's very very handy.