I called QuickBooks support just now and I was told that despite the "New training and exam for QuickBooks Desktop 2020 certification and recertification is now available." message at the top of the course list, I'd have to wait for the desktop courses to post and that I'd get an email about that when that happens.  I asked if they had a timeline as to when that might happen and they told me by July.  So despite the "now available" message they apparently won't actually be available until sometime in the next few months.