Secret Field

The value sits in a read-only input rather than a disabled one, so it can be focused, selected and read, and focusing a shown value selects all of it for copying by hand. The field's state — shown once, hidden, revealed, gone — is a sentence attached as its description, never a colour or an icon. Copying is announced through a status region that exists before the first copy, and failure is announced too, with what to do instead, because the clipboard can be refused. Every button carries the field's label in its name, so a settings page with several keys has several distinct Copy buttons. Regenerating is confirmed inline in a named group that states the consequence, since it revokes the current key.