First open up the /Saved_Data/ map in your "Supreme" folder.
Then open up "Avaiable_Levels.txt" and change the offsets to:

{
"Easy",1,
"Medium",1,
"Hard",1
}

Save and exit that file.
Then open up "Defaults.txt".
Change the line that says:

available_tracks = 3;
to
available_tracks = 7;