In Kleopatra the details dialog now has a button "add email address" but requires name and email and talks about UserID and how the UserID will be presented.

A user made this suggestion:

so let's take my present case. By clicking on "add an email" the GUI should show me the following steps. ) It's a draft: 1) A confirmation about the key I want to manipulate 2) A new filed with a title Add your second email address here: 3) A questin if I want to use the same user name for this second email address, if not a new field where I will be able to write the new user name for this second email address 3) An overview of the
changes that will be made 4) Confirmation with execution of changes.

IMO this is a bit too many steps but I would have to play around with it a bit.