Apple Final Cut Pro X (10.0.9) - Manual (Page 250)

Chapter 10 Add transitions, titles, effects, and generators 250
3 In the Timeline, choose either Select or Range Selection from the Tools pop-up menu in the
toolbar (or press A for Select, or R for Range Selection).
4 Drag across the area in the Video Animation Editor where you want to adjust the effect.
5 Adjust the effect within the range by dragging the effect’s horizontal control up or down.
Keyframes are automatically created along the adjustment points within the range.