Official comment
@nicole, Not true! It's easy to resend to non-openers in Ontraport and you definitely don't need a tag!
Instead of explaining all the different ways you can do that, I'll suggest that you share you specific use case with the Facebook community (https://facebook.com/ontraportusercommunity) and you'll get plenty of input that will save you tons of time. It'll be helpful if you explain your goal and current process there.
Just as a quickie: did you know you can click on the number of 'not opened' or 'not clicked' in the messages collection and get directly to that list of contacts, no tags required!?