This is a first post in pre-1900 for me so bear with me.
The POD has been discussed before, but there it is. We have a Norwegian King of Scandinavia that we did not get OTL. Following the coronation of King Olaf and the formation f the Kalmar Union the possibilities are open.
Lets assume that King Olaf maries into one of the most powerfull swedish families forming a true interscandinavian dynasty. Thus, the assumption is (to the extent possible, lets try to keep this assumption seperatefrom the discussion on the points below) that we this way get a internally stable Kalmar union.
What would this Union do from here?
Consolidate against Finland/Russia?
The Baltics?
The Hanseatic states?
Alternatively, King Olaf with a norwegian descendant could be more inclined to look at the Atlantic where Britain is in the way and Danish lands a few hundred years earlier?