I'd say having the "Remove Certification" action when a certification is selected does make sense.

Having the "Add Certification" option when a certification is selected is indeed confusing and should be disabled

Try it. It does not do what you think ;-)
You will revoke the certification of the User-Id and not remove that one certification. I should have taken a better example for the screenshot:

I would propose two more changes to make the dialog behave in a way that seems logical to me:

• Only show the most recent certification/revocation by each respective certificate
• Make sure that in the dialog that opens up when clicking "Revoke Certification" on a *User ID*, only the most recent certification by each certificate shows up

Then it makes sense to keep the "Revoke" action when clicking on a certification (to revoke just this certification) and when clicking on a user id (to revoke all certifications)

Very good suggestion! +1
I believe Werner and Alexander will agree, too, as we talked about that tab the other day and that showing only the last certification would be preferable

Implemented in https://invent.kde.org/pim/libkleo/-/merge_requests/130 and https://invent.kde.org/pim/kleopatra/-/merge_requests/275.

• Hide/Disable the certify action when a certification is selected
• Show only the most recent certification / revokation in the list and in the dialog showing which certifications will be revoked