If you're using the QuickBooks Solopreneur subscription, transactions can only be excluded, not deleted. Excluded transactions won't be included in your tax calculations or reports.
However, if you exclude transactions that were added manually or imported from a .CSV file, they'll be permanently deleted. (This is the warning prompt in Step 3.)
Here's how to bulk exclude transactions in Solopreneur:
Go to Transactions, then select Bank transactions.
Check the box next to the downloaded transactions you want to exclude.