As I said in another post, I found a way to use my nanoKontrol: as a mixer in Ableton Live
But to have it working, I had to use the Korg editor to set the 2 banks buttons properly because, quite oddly, their default setting was not to be the 2 banks buttons 
Then I found a way to use my MidiMix to drive the sliders in my GSi VB-III v.2, and that plugin ONLY, so now my set to jam with the Hammond is completed, and tonight I jammed with the Hammond until dropped from exhaustion 
So here is how I did it
To have a controller dedicated to one instrument only, you should go to Options > Link and set as “None” the controller you want working for a single plugin
If you set the MIDI Mix as the nanoKontrol instead, they will both move the other controller sliders, that is a mess
In my case, the controller for the Hammond is the MIDI Mix because it has 9 sliders, like the upper keyboard of the Hammond (plus many buttons and knobs that I still have to map to the plugin)
The NanoKontrol 2 instead has just 8 sliders, compared to the 1 version that had 9, so it is more suitable to be the Ableton mixer
And now the routing I used to jam tonight
BTW: The cool thing in Ableton is the easiness to show the routing, while in Bitwig it could have required many screenshots
As you see, Scaler 2 sends chords to a MIDI track that resends them to the Hammond lower keyboard (Channel 2)
Now, having read that in Ableton you have to use a rack to have one controller driving exclusively a plugin through the “Lock To Control Surface” option, and lacking apparently a way to create an instrument rack (just a drum rack) I grouped the plugin (linked to my Alesis keyboard, using the Channel 1 to send the solos on the upper keyboard) and a MIDI track linked to the MIDI Mix to be able to move the sliders, and the “Lock To Control Surface” was not there again
Well, I tried my pseudo-rack anyway, and I found it worked, even if I suspect it may works even without the grouping 
Anyway, now I can play my solos on the Hammond upper keyboard while Scaler 2 sends riffs on the lower keyboard, and I can also move the Hammond sliders, BINGO!
N.B: to have the solos in scale I use one or two Ableton scales, a thing that I always missed in Bitwig
The last scale (just before the plugin) matches the scale used by Scaler, while the first scale is almost always different and found by ear
I then added a MIDI Polysher before an UJAM guitar, and added my loyal Broomstick Bass to have bass & drums
With a set like this you can audit the whole gazillion of Scaler riffs, then you have just to match the last scale before the solo instruments, and it’s done!
You can jam forever, changing on the fly the sound of the Hammond or the other instruments: a pure joy
