Technically, Fred, you're correct: "you" is the complement rather than the object. But in English it sounds excessively formal and old-fashioned to say "It is I" -- we would normally say "It's me." And in French you never say"C'est je" or "C'est tu" but "C'est moi/toi", even though "toi" in other contexts is the oblique case of the pronoun. So I guess it's probably the same in Danish. I see that Indra927477 made exactly this point 4 years ago on this discussion page.
I'm Italian and these sentences are clashing with my idea of an object pronoun because in Latin (romance) languages the verb to be doesn't allow any object like some other verbs. probably in Danish it is so, like in spoken English. so it's ok. but when we speak of grammar "you" is not an object in this question.