i wouldn't bother with the dates. your only option is to delete the import and reenter manually. or change the 8949 check box - line 1a - on each one.
another option is just to enter summary amounts for the various types. you'll need to enter M in line 18a and $0 for 18b. then you can complete form 8453 checking the 8949 box. this will require you to mail in copy of the sales schedule (1099-B) with a copy of the 8453 and follow these instructions:
If you are filing your tax return using an online provider, mail Form 8453 to the IRS within 3 business days after you have received acknowledgement from your intermediate service provider and/or transmitter that the IRS has accepted your electronically filed tax return. If you don’t receive an acknowledgement, you must contact your intermediate service provider and/or transmitter.
Mail Form 8453 to:
Internal Revenue Service
Attn: Shipping and Receiving, 0254
Receipt and Control Branch
Austin, TX 73344-0254
