Well, I had the same problem when I explored the SDK and wrote my tutorials. If you check them, there should be explained how to add variables with hand, and give examples step by step. You won't cause havoc, and you can test it with the dialog editor. (But ofc, it's still a pain in the ass to add variables manually.)
My buggy dialog editor version was the one released with Reloaded source (the first release, not the second.)