In more recent years, the IRS uses the codes from the 8949 to determine it is a summary. 

As long as you have code M entered, the IRS will know to look for the attachment either with the 8453 or  in the PDF attachments. This article gives a pretty good overview of how to do the attachments with the new format in ProSeries 2020 https://proconnect.intuit.com/community/form-1040/help/how-do-i-attach-a-stock-summary-to-the-schedu...