I've made this mistake a few times over the many years I have been using Quicken. I know that the general suggestion here is to restore from a previous backup, which is how I typically deal with this, but the last time this happened was kind of a "last straw" for me, as this is an easy mistake to make, but very much a PITA to correct. It seems to me like this should be easy to correct - there should be a simple way to unmatch a downloaded transaction even after it has been matched and accepted, provided you are still in the process of reconciling a fresh download.
So my first question is whether or not there already is a way to do this which I have somehow missed for the last 20 years, and if not, why not?? Is there any reason that I am missing as to why this would not be a good feature to request?