Maybe the family of the child has visitors and they are showing around the house to them. Like "here's the balcony", "here's my room" etc Δείχνω means "show" but it can also mean "point to/at". For example: "δείξε μου το βιβλίο σου" means "show me your book" and "σταμάτα να δείχνεις, δεν είναι ευγενικό" means "stop pointing, it's not polite". The child here is probably showing around.

I've reported this in other cases. There are a few of these. But yeah, you need to show someone the balcony.

I agree. It makes no sense. I don't think it would ever be said in English. "The child points to the balcony" makes more sense. Or maybe, "The child shows them the balcony".

Some of the hints are like that. "Acc" stands for "accusative", "n" for "neuter". Of course, "accusative"="nominative", since it's a neuter noun.

The tiles for answering are generated automatically, at least partly from the hints -- and the hints sometimes contain not only translations but also little notes to the learner such as "acc" for "accusative case".

Those shouldn't really turn up as tiles but Duo isn't smart enough to tell them apart from the translations, unfortunately.

In the sense of "to show sth to sb", yes, an object is needed in Greek as well. However, "δείχνω" can also mean "to point at", so perhaps that would be a better translation for this sentence.

So in the newspaper this grammatical construction is wrong? I mean... when you read it as a native speaker, sounds this strange to you? Just asking... I'm not a native speaker, so I'm deaf (grammatically) to heard if it sounds wrong.