Hello @NancyB0316 ,
At the moment there isn't a way to tab / indent for paragraphs and sublists in the email editor. This is something our engineers are working on for mobile-compatibility, so I got your case submitted to them. As soon as they have an update to the feature request, they'll make sure to reach out.
In the meantime, I'd recommend you make sure your paragraphs have a line of space between them to help keep them visually separate. For sublists, you'll likely need to either take a screenshot and insert it as an image block , or you'll need to redirect to a document.