Flags the frame for automatic saving and restoration of position and dimensions. The position and size of frames so flagged is automatically saved when the UI is shut down (as when quitting, logging out, or reloading) and restored when the UI next starts up (as when logging in or reloading). If the frame does not have a name (set at creation time) specified, its position will not be saved. As implied by its name, enabling this property is useful for frames which can be moved or resized by the user.

This function is automatically called with the value true when frame:StartMoving() is called.

In order for the saved position to be applied to the frame in later sessions, the frame must have been made movable with frame:SetMovable(true).