How to merge items?

I have had an account to a specific web site for long, it includes the usual user/password, 2FA and, since a few years, a passkey.

This morning I logged in to the site with a new device, so had to go through authentication from scratch. The passkey did not work in the sense that neither the site nor 1Password proposed to use, which, from hindsight, is strange. Why so?

Anyway, I logged in with user/password/2FA, and I got a pop up asking me whether I want to install a passkey. It was early morning, and I had forgotten the existing one, and I said yes.

The result: I have now two entries on 1Password, with the same username: one which contains a passkey entry, the other the old one, with password, another passkey, and some other notes of mine.

Two questions:

• is it so that the new passkey overwrite the old one (I would think yes)
• how can I merge the two entries on 1Password, essentially replacing the old passkey entry with the new one? Watchtower does not flag these two as duplicate items, so it does not help.

Thank you

Ivan

P.S. One of the paskeys is working properly; I tried to log in from another browser that I never used for amazon before, and it worked by asking me to read a QR code to log in...