from the 2017 S123 site:
Survey123 for ArcGIS 2.0 Beta Program is now open
"As of Survey123 2.0 editing functionality as described above will be limited to Surveys without repeats. We will not support editing attachments either in this first round. Editing surveys including repeats will come later in a 2.x update."
can someone confirm that this still not possible to retrieve a record from the Inbox and add attachments?