The only way seems to be to search for the note, and then do a MultiEdit "Delete = yes". The problem comes when the search throws up more than one task which matches! Then you have to figure out what makes one task different from another, so that you can create an artificial search which just delivers the task you want to delete! Imagine you find you have 2 identical tasks in the same folder - then it's impossible to create a search which separates them!!
Surely there's a better way to handle this? Please.
Did you try the trashcan button, (it should be on the far right side)? If you don't see it, enable it by going to Account Settings -> Fields Used, and then selecting Trashcan. If this isn't what you mean, I'm not sure what you are talking about.