It is difficult to say anything definite about the status of the office at that time, but sources from the 14th century shows the width of the power of the Lord High Steward.
[1] The steward was the king's closest confidant and during the guardian regency at the time of Magnus Eriksson's adolescence (1319–1331), the title holder (mostly Knut Jonsson) was the mightiest man in Sweden.
After Jonsson Grip had died in 1386, no new steward was appointed until 1435, when the noblemen forced king Eric of Pomerania to do so.
[2]Sweden suffered from political turmoil under the regency when Charles XI's was still a minor, which brought about changes to among others the Lord High Steward and the other Great Officers of the Realm.
The significance of the office had decreased when Magnus Gabriel De la Gardie got the position when Per Brahe the Younger died.