The following in shown in the HELP forum FAQs:
"Can I take a move back/reinstate a timed out game if my opponent agrees?
Unfortunately, no. Once a move has been made it cannot be taken back. . ."
Hopefully, without insulting peoples' intelligences, if your opponent agrees with you, then after you made your unwanted move, your opponent can make one move; and then, both of you simply put your moved pieces back to the squares they came from as the next half moves.
This takes up half moves, but your position has been put back to where you have wanted it. Just keep in mind, it can count as a repetition of position for drawing purposes and that you will be putting your trust in your opponent to follow your agreement. Otherwise, it is very simple to do.