Are you wanting to use the new field you add to the attribute table in a survey as well, or you just want to use it in other products? If you don't plan to use it in your survey, or the existing survey, then yes, you can add to the attribute table without needing to add to the survey. It just means that field will not be visible in Survey123 Connect or the field, or the web app for users to enter data.
No I don't want to use the new field in the survey. However I do want users to use the new field in the web app. I am basically wanting users to be able to go into the web app and add comments to survey responses. So I am hoping to create a new 'comments' field if possible.
When I bring the hosted feature layer created by the Survey123 form into a web map, I want to be able to add a field to that layer that doesn't appear in the survey form itself, but allows people to add comments in the application.
I have had a research into this and think this functionality is available in Enterprise 10.7?
I just checked with a 10.5 site - you can add a field when a layer is in the Map View. Open it's attribute table and open the 'Table Options' menu. If it's a hosted service, you should see a 'Add Field' option.