Hi. There is no easy solution to this because it is not possible at this moment to instruct Survey123 to always execute a calculation such as pulldata("@property","username") when the form loads. The username question type does not do the trick either because it will not override an existing value.
If you wanted to store the logged-in username editor tracking would the best option. If at all possible, I would try to eliminate the proxy with embedded credentials.
As a workaround, you could use Power Automate or Integromat to process data submitted from Survey123 and automatically insert the logged-in user name in an attribute of your layer. The Survey123 payload carries an object caller userInfo which includes the username, email and friendly name of the person logged-in to the app. You can use this information to make an HTTP request of your layer to update an attribute.
