I messed up recording a paypal transaction and could not get the transaction download to match up with it so deleted the transaction from QB and reentered it correctly. Could no longer get QB to recognize the transaction on subsequent downloads. Editing the FTID in the qbo file did the trick.
This is a valuable workaround for what I think QB should make possible in a more straightforward way. Perhaps QB tech support could have given user12372 some effective help if there was a formal interface to do this.