The most obvious would be a different Battle of Bornhöved, with Denmark solidifying contol over the northernmost German duchies north of Elbe (Emperor Frederik II had already accepted Danish 'ownership' of the area).
And then go from there, following the obvious track that both Denmark and later Sweden tried following, making the Baltic a private lake ... Helps that Denmark can also press on from Estonia which they owned at this period of time, so it shouldn't be to farfetched that they could convince the teutonic knights to move on, further east into OTL Lithuania, with Denmark bracketing them, to the north and west, with Poland to the south.