Not strictly a keyboard shortcut, but you can make a link a game link be to a particular numbered move by adding /{insert move number} to the game url. So for example
https://online-go.com/game/425048
goes to game number 425048, and
https://online-go.com/game/425048/92
goes to move 92 in that game.
See https://forums.online-go.com/t/new-feature-skip-to-move-with-url