OK, I think I have a workable approach that the IRS won't have trouble with. I assume that virtually all the transactions are "Box A" "Short term, Basis reported to the IRS". For those transactions, fill out one line of 8949 labeling it "Box A transactions at eTrade (or whoever)" For purchase date "various" for sale date 12/31/2017. Enter all the codes and adjustments amount as shown the broker's totals.
If you have any transactions other than Box A ones, then enter them individually.
Since the detailed info for Box A transactions has already been sent from your broker to the IRS computer, I think that will work out fine.
