We fly in at 10:00 pm on a Saturday night in April and leave for Home Sunday at 1:00 pm
Is it possible to see anything worthwhile in 3 hours on a Sunday morning?
You can see Nyhavn
https://www.visitcopenhagen.com/copenhagen/nyhavn-gdk474735
Sure it is. Where are you staying and can you store your luggage at your hotel?
Thanks for the input No hotel yet. Deciding between airport and center city
Copenhagen Airport is only 20 minutes away from the city centre by train or metro, so you could stay in one of the hotels near Kongens Nytorv and use you sunday morning to have stroll along Nyhavn.