It’s a two-stage operation…
1)
Select the MIDI Part, then, MIDI Menu>Functions>Extract MIDI Automation.
You should now have an active Automation lane for CC#1 (you’ll see the curve, and when you hover over it, you’ll also see the individual nodes)
2)
Open a 2nd automation lane, and set it to “Velocity Shift”
Using the Range tool, select all the CC#1 automation, and just drag the selection down to the Velocity Shift lane.