I am having the same issue, having to individually delete each transaction is ridiculous.  It would be great if you could add some actual QB users to your development team.  This is a very basic function.  I have already left feedback for this feature and other very intuitive features that are lacking in QBO (undo reconciliation).  I need to delete several years worth of transactions that were downloaded when I switched from Desktop version, there are literally 10,000+ transactions that will take days to delete manually one at a time.