Sonar Platinum -- How to draw in new midi velocity data?

Hi, I am probably missing something which is really obvious to others -- after a bit more hunting around the program, the manual and google than i'd expected, I still can't seem to draw in new midi velocity data, as envelopes, controller bars, or any other way.
 
In the piano roll view, I can use the Draw tool to scale existing velocity data, but not to draw in new velocity data (as my reading of the manual now seems to confirm.).(If true, gosh, why?)
 
In the track view, creating automation lanes, I've drilled down into every list and sublist of assignable midi envelope parameters I can find. I see pretty much everything under the sun, but not velocity.
 
Thing is, I'm positive that the other day, in track view, I did see velocity as an envelope assignment as a sub-choice for a midi track, but can't replicate that now.
 
Sorry, I thought this would be an easy one. I've spent most of my learning curve in audio and am only just now getting to midi. A quick steer would be much appreciated!

I see, thanks.  I had just assumed that if you could draw in, say, volume envelopes in spaces with no underlying midi data, you could do the same with a velocity envelope -- sending in effect the command, "Ok, when there's no midi data, no harm done, but when there is midi data, play it at whatever is the last velocity stated is."  

A note-on event consists of three bytes. The first has four bits for the command type and four bits for the channel. The second byte specifies the key number, and the third byte specifies velocity.
 
You can't have a note-on event without specifying the channel, key number, and velocity, so the bottom line is velocity cannot exist without a note-on event.
 

We can put changing dynamic levels on a single note in a VST3 in Cubase.
Can we not create that kind of expression mapping in SONAR?

Thanks for the clarifications, all! Thought I was going mad. (Might be, but that's just not one of the symptons.)
 

Bob -
 
I've found other useful tutorials there too. I need to search through them again.

Great link Bob, thanks for that.
 
Notice however that all of the techniques described are still only acting on the velocity of a single note.