I recently was trying to create and add a passkey for a site that I had an existing entry in EnPass. Normally when I do this, it offers to add the key to the existing entry. However, recently I had a site where this wasn't occurring. It kept offering to create a new entry instead of offering to add to the existing entry. It turns out that the URL I had in the existing entry was just example.com instead of www.example.com. Once I added the www to the front of the URL, then it finally offered to add the passkey to the existing entry. In my opinion, if only the domain is in the URL field, it should offer to add a passkey to that entry even if it's from a subdomain. I imagine detection to offer a passkey to a site might also be based on this logic, although I have not tested and confirmed.
Also, there should be a way to merge two entries. For example, once or twice (including this time) I accidentally created a new entry for a site when adding a passkey instead of adding to the existing entry. I should be able to merge the two entries so that the passkey is added to the entry that already existed.