Hi there
as I said many times, the Keys-Loch feature didn’t work well/always for solos for me
In Ableton Live I used the Scale tool, while in Bitwig I used Key Filter that worked both well, but not being in sync with Scaler’s moving chords they sounded odd sometimes
Now that I am a new happy user of Cantabile, how doing solos?
Well, using black keys and a few of whites works quite well 
, but maybe I found another way to use Scaler’s Keys-Lock
Instead of muting Scaler output and using Chord Notes or Chord Extension, I leave the output unmuted, I deselect DAW Sync and Loop, and I use Keys-Lock White Keys
If you do that, Scaler will not play the chords in the series, and you can use for your solos ALL the white notes that you see below, having as a limit just the size of your keyboard
Moreover, if you select Section B instead of C, you can also change the scale on-the-fly, manually or automatically
I think to remember I found this trick last year, but I was unsure it was a real hidden feature, or I was just stoned 
but now I tried the trick with different series of chords, i.e. the embedded ones, the Suggest(ed) ones, or series built-up manually, and I am quite sure it is a hidden gem
try it and let me know if it works for you
I forgot to link a song to let you understand the power of Section B for solos Cantabile 1st