Ok i got it. It does work only with the channel strip compressor !
It does not work with the channel strip gate, nor does it work with channel plugins. So this is not terribly useful, except if the channel strip compressor is used exclusively.
More, i feel that channel gain reduction is something that should be shown in the lower part of the mixer, near faders. And this is how other software editors did it.
The logic suggest that we should have pre fader meters in the upper side of the mixer (meter bridge), and post fader (or post panner) meters with gain reduction indication in the lower part of the mixer, near the faders,
If we could have a gain reduction and a crest factor meter near each fader, this would be nice, and better than the competition that show only the gain reduction. The two could be inline, each one with a different color, to save channel width room. Short bargraphs are ok for this use. See the SSL channel strip, only a few leds.
Gain reduction should take into account all plugins. This is quite easy to do even without specific VST support, comparing the channel input signal with the channel output signal and make a subtraction.