Action Sheet
TIP
Small circles in the timeline represent keyframes.
Scroll / Zoom
Same as main canvas.
Select a keyframe
Click a keyframe to select it.

Shift Select keyframes
You can also select keyframes continuously by holding Shift and click.
If the targets have been selected already, Shift + Click will clear the selection.
All Select keyframes
Press a to select all keyframes.
If all keyframes have been selected already, pressing a will clear the selection.
Delete Keyframes
Press x to delete selected keyframes.
Grab
Press g to start the operation to grab keyframes.
Then move the mouse to move their locations.
Finally, left-click to complete or right-click to cancel the operation.
Duplicate
Press D to duplicate keyframes, and then enter grab operation automatically.