The assignment of the "Observer" role is only possible via the API, when declaring the "TransactionSigner" structure.
You will find the details of this mode of integration in our guide, by following this link:
The "signer" is able to view and sign documents. The "observer" only intervenes to monitor the collection and display the documents to be signed and those already signed.
You can also activate or deactivate the "finalDocObserverSent"option, which indicates whether observers receive signed documents by email when the transaction is completed.