Thad: No such button is needed. Currently you have the option to have the move list displayed next to the game. Every move is clickable. It's already possible to view a game move by move (ply by ply even).
(esconder) Mantenha a sua Caixa de Mensagens limpa, Arquivando mensagens importantes e usando regularmente a opção "Apagar TODAS as Mensagens". (pauloaguia) (mostrar todas as dicas)