A while ago I posted on softwarerecs and asked for a program that did X. An answer came along and suggested a program that did X very well, and I accepted the answer. However, after a few months I found myself dissatisfied with this program because I had never considered the need for it to do Y. In short, "It's just what I asked for, but not what I wanted."
So what should I do now? It seems wrong to retract the accept and edit my first question, but if I ask a new one, it probably won't add to much the site, as ~70% of it will just be copied from the original question (I still need it to X, after all).