I have transferred the registration of a few domains to CF but I can’t see a list of them anywhere.
From the Cloudflare Dashboard (dash.cloudflare.com), you can click on the Domain Registration link. It will show you a list of domains you can transfer, then a link of “Show nn domains unable to transfer.”
That will show you the domains already registered at Cloudflare.
Very strange! I’m sure when I looked at that this morning all it showed was one that I could transfer and the 10 that weren’t transferable. Having transferred the last one that could be it now shows all 4 that have been!