My data is too extensive and complicated to enter by hand. Will TurboTax import .txf files and, if so, what data columns are necessary?
Consider the "Summary" option.
IRS requires details to be listed on Form 8949, or on your own forms (e.g. consolidated 1099-B) which have the same information and in the same manner as Form 8949.
Either way, if you choose to summarize, 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 (Day Trading) or Category D, Form 8949 is not needed for transactions without adjustments. No mailing is necessary. TurboTax won't ask you about wash sales if you don't check the box.
If you have wash sales, it gets more complicated since those have to be itemized on Form 8949 and the summary totals adjusted accordingly.
Enter the wash sales on Form 8949, then use the subtotals on the bottom of that form to know how much to subtract. Be sure to NOT check the adjustments box in the summary window.