The first handle controls how the move leaves its starting key. The second controls how it arrives at the ending key. A flat handle gives zero speed at that end of the move.
Press anywhere in the card and drag. Curvy chooses the nearer handle when you press, then moves it by the distance you drag. You do not need to grab the small dot.
The card changes during the drag. The curve is kept when you release. With Apply as you edit on, that completed drag applies to the selected keys as one undo.
Keep an end flat or mirror both handles
Hold Shift while dragging to keep the moving handle on its endpoint’s horizontal line. A handle also snaps gently to that line when it gets close.
Hold Option on Mac or Alt on Windows while dragging to mirror the other handle through the center of the card. Add Shift for mirrored flat handles.
Moving a flat handle farther horizontally from its fixed endpoint increases its influence. The animation spends more of the segment slowing down or speeding up at that end.
Add overshoot or anticipation
Drag a handle above the ending value or below the starting value. The plot scales to fit the curve itself. A handle beyond the visible range is shown at the card’s edge. This can make a value go past its destination or move backward before heading forward.
Opacity, Scale and other nonspatial values can take these curves. Unseparated Position needs the Position overshoot workflow.
Preview and reverse the curve
Click the card without dragging to play its small motion preview once. It stops when finished. This does not apply anything to the timeline.
Right-click the card and choose Flip to reverse the held curve in time and value. An ease that favors the start becomes one that favors the end. With Apply as you edit on, this edit also applies to selected keys. To apply a flipped version while keeping the held curve, use the Apply modifier.
For exact influences or a CSS curve, type the numbers.