I have about 1400 transactions in my 1099-B statement which turbo desk failed to import from my brokerage. Subsequently, I thought of entering the summary manually but turbo tax gives me error that "Value is too large for this field. Please enter smaller amount". My Gorss Proceeds for box 1D are over $14 Million.
TurboTax Online can only handle 500 transactions, while Desktop should handle about 2,000, although downloads with that many transactions sometimes fail. Instead of downloaded individual transactions, you can enter summary totals, as you mentioned. When entering summary totals, there is a workaround when gross proceeds (or cost) exceeds $9,999,999.99. Split the category in to multiple transactions. For example, if your Short Term transactions reported to the IRS (Box A) totals $14,000,000, simply split it in to two summary transactions of $7,000,000 each. It's a little more to enter, but it beats entering 1,400 transactions.
For information on entering Summary Totals, see the following FAQ: