Each game of Platforms of Goo has 9 save files, but there's no way to clear a save file in game, which you might have to do for certain full-game categories.

To find where the profiles are stored, first find where the "Platforms of Goo" folder is saved with the executable file and game assets. In my case it's in "C:\Program Files (x86)\Platforms of Goo". If it's the same for you, all the profiles should be in: "C:\Users\USERNAME\AppData\Local\VirtualStore\Program Files (x86)\Platforms of Goo\res" (replace "USERNAME" with your PC username).