It is always possible to edit an ongoing transaction if the person has not signed the document. It is also possible to change in an ongoing transaction with several signatories if the person / persons have not signed. Just click on the person where you want to make changes (see image below):
From here, it is possible to edit Recipient details, Signature method, identification method, expiration date of the transaction and to send a new notification to the user. It is also possible here to add a signer to the ongoing transaction.
This is also, where it is possible to abort an ongoing transaction. It is thus possible to abort a transaction with several signatories, if not all parties have signed.