A won order can only be moved between won and lost stages. To turn it back into an opportunity, copy it as an opportunity and delete the won order.
- Open the won order and click Create copy at the bottom (see Create a copy of the order).
- In the copy, change Stage to a stage with a probability below 100%. Set the Close date to when you expect to win the deal, and save.
- Delete the won order. Until you do, the deal still counts as won.
Custom fields that you can't see or edit are left empty in the copy. Check the copy against the original before you delete the original. If the order has been synced to Fortnox or Visma, deleting it in Upsales doesn't delete it there.
No Create copy button? An admin has turned it off with the order standard field Copy button.