Keyframes Panel
From Synfig Studio :: Documentation
The Keyframes dialog is where you make new keyframes for the animation.
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These will show up in the Timetrack dialog. To jump to a specific keyframe, double click on the (JMP) column.
The 'add keyframe' button adds a new keyframe to the current frame - a frame where there is no keyframe set already.
'Delete keyframe' removes a keyframe.
The 'duplicate keyframe' button copies the keyframe to the current frame.