If you edit a preset, but decide you do not like your changes and would rather return to the previous settings, you may simply select another preset without saving. This way when you return to that preset, it will recall the settings as they were before you started editing. This method works as long as you did not save your unwanted edit.
If you did save your edit and would like to return to the original factory preset for that preset location, but do not want to perform a complete factory reset (which would overwrite ALL preset locations with the original factory settings), you can hold down both of the BANK UP and BANK DOWN arrow keys simultaneously, until the display reads "Pr". To restore the original factory settings for this individual preset only, hold down the applicable preset button (A, B, C, D, or E) for approximately two seconds to save.