You can adjust the automation data for an entire track in one go. If the track is part of a group, and if the relevant settings are selected in the Groups inspector, the track automation data across all tracks in the group adjusts accordingly. However, the relative parameter values of each track are maintained.
You use the trim behavior in the track header to adjust automation points for:
An entire track
A partial selection (marquee) across a track
Multiple selected tracks
Multiple selected subtracks
After making your selection, place the pointer over the numerical display in the track header (the parameter value changes to Trim), then drag vertically to change the value (the offset or trim amount).
Tip: If the Trim field is not visible, position the pointer over the line dividing the track headers from the left edge of the tracks, then (when you see the Resize pointer) drag the line left or right to resize the track headers.
When you release the mouse button, the numerical display reverts to showing the value of the active automation parameter at the playhead position.