This is how I select just a section of automation points and change the values in the Event list (although I also want to be able to scale them, not just add or subtract values in a linear fashion -- Transform is likely the way to go for scaling).
1) In the Main window, select your MIDI region, press a for automation mode, and zoom in to the area you want to edit.
2) Open the event pane and make sure you're viewing the midi note and automation events.
3) In the midi region, while holding down the Shift key, click and drag across the section of points you want. You can select multiple, discontinuous sections by highlighting one section, releasing the shift key and mouse, then repeat for the 2nd section, 3rd section, etc. These events all become highlighted in events list. Release the shift key and mouse after selecting your final section.
Have to get this next part right, otherwise the events you want will be de-selected.
4) Hold the shift key, and in events list, click ONE of the highlighted events -- the highlight for all selected events will now change color and turn blue. Release the shift key.
5) Click on the Val column for one event and drag up or down. ALL of the event values change.