From the manual p.488
"To raise/lower selected envelope nodes
1. Set the track’s Edit Filter control to the desired automation parameter (Track Automation or Clip Automation).
2. Do one of the following:
• With the Smart tool, position the pointer near the top center of the track/clip, then drag up/down.
• With the Edit tool, position the pointer near the top center of the track/clip, then drag up/down.