First make a backup copy of the file "Available_Levels.txt", which is located in your Supreme/Saved_Data folder. Then open up the original with any text editor and make the following changes:

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

Save and exit, and make another backup copy of the file Defaults.txt. Open the original with any text editor and make the changes below:

available_tracks = 3;
to
available_tracks = 7;