I know the Survey123 Connect Desktop app can split surveys into sections but I'm not (readily) seeing the same capabilities in the web surveys. Thanks!
A workaround: you can use the Note question in Survey123 Web Designer to mimic the behavior of separating your survey questions into sections. Simply leave the label property blank, then add some text in the hint property - and you can center the text, so it looks like a section header.
Hope this helps,
Retrieving data ...