For select_multiple questions you should have the raw data entry (choice names) meet the requirements.
https://doc.arcgis.com/en/survey123/browser/create-surveys/quickreferencecreatesurveys.htm#ESRI_SECT...
Question names and choice names should not contain special characters, such as spaces, commas, hyphens, parentheses, brackets, or characters such as $, %, and #. It is important that choice names for Multiple select questions do not contain spaces or commas.
So your raw data being submitted into this question won't appear nice, but will function correctly when being submitted (or later edited). You can't really change the way this data is stored directly.
I want to see my selected choices separated by Bullet Points instead of Commas (Selected choices attached).
You could process the data within the survey but it depends on what and when you want to see the 'bullet list'. When do you want to see this? Within the survey? After submission but immediately? Where? A report, the Survey123 website, a web app, the downloaded data?
e.g. you could use JavaScript function within Survey123 form to process the comma-separated values from the multiple select question and return them as html driven bullet points. This would look OK in your survey form but then exporting to excel it'd be a mess of html tags.
