IRS requires all transaction detail on form 8949 or on your own document (eg consolidated 1099B) showing the same detail and in the same manner as 8949.
If you choose to summarize, or your broker is giving you only a summary (this would be unusual) you have to mail the transaction details to the IRS within three business days of IRS accepting your tax return.
Exception
: if you summarize Category A or Category D, Form 8949 is not needed for transactions without adjustments. No mailing is necessary.
As an active investor, be aware that your category Box A sales without adjustments do not require Form 8949, so there is no reason to import or key in those transactions.
instead use the "enter a summary" option to put your numbers on Schedule D Line 1a.