Stuck in SSE

[Blips]

I've just finished killing all the bosses in "The Great Maze" but now I have no idea what I should be doing to advance the plot. Whats the next course of action?

 

[Pnuts]

double check the map, any dot on the map without a line is a door you havent accessed yet

 

[GigaRidley]

Go back to the Donkey Kong area in the maze (where there is a high updraft with the leaves) and enter the door with the large blue arrow pointing to it. Then enter the door in the middle (you see in in the background) in that room to fight Tabuu.