If you are attempting a new import and only want to test with on transaction or perhaps you might see a transaction that you do not want to import into QuickBooks using Transaction Pro Importer ("TPI") you can easily remove these lines from the file contents screen within TPI.
When you get to the file contents screen (which is the second screen within TPI) select those rows that you do not want to import and select the button, Delete Selected Rows.
In the example below since it is our first sales receipt import we only want to import the first transaction that has refnumber of 101. So we highlight record #s 3 - 11 and then select the button, Delete Selected Rows.
Then you will see that these rows have been removed from within TPI.