Propagate
Mode
Pose Mode
Menu
Pose ‣ Propagate
Hotkey
Alt-P
The Propagate tool copies the pose of the selected bones on the current frame over to the keyframes delimited by the Termination Mode. It automates the process of copying and pasting.
Modes which determine how it decides when to stop overwriting keyframes.
Defines the upper-bound for the frame range within which keyframes will be affected (with the lower bound being the current frame).