Answer: Elderberries, given their size, have growing habits that include suckers, and a preference for a moist location. That doesn’t sound like the best fit for potting on a tiny, hot balcony.
Elderberry plants tend to grow like a thicket, with suckers, and they spread out, so I think they would fail to thrive in such a confined situation. They also tend to grow quite large. If you have a small balcony it might be a bit overwhelming.
You can give it try but it would probably not survive the winter in the pot unless you have a place to keep it so the root ball does not freeze.
Hope this helps,