the easy way is with windows. You must have winiso and winimage.
open knoppix3.2.iso with winiso. Extract boot.img
Open boot.img with winimage
extract and edit syslinux.cfg (add your cheatcodes near the cheatcodes already there)
add (copy) the edited syslinux.cfg to boot.img and save
open knoppix3.2.iso with winiso
menu bootable cd
load boot.img (boot.img c:\somewhere\boot.img)
menu file
save knoppix3.2.iso (with new boot.img already loaded)
burn knoppix3.2.iso

NB: It is not necessary to copy the edited boot.img into the cd,
but copy it if you want (with winiso)


A fragment of syslinux.cfg already edited

DEFAULT vmlinuz
APPEND ramdisk_size=100000 init=/etc/init lang=us keyboard=es xkeyboard=es screen=800x600 floppyconfig apm=power-off hda=scsi hdb=scsi hdc=scsi hdd=scsi hde=scsi hdf=scsi hdg=scsi hdh=scsi vga=791 initrd=miniroot.gz nomce quiet BOOT_IMAGE=knoppix
TIMEOUT 300

PROMPT 1
DISPLAY boot.msg
F1 boot.msg
F2 f2
LABEL knoppix
KERNEL vmlinuz
APPEND ramdisk_size=100000 init=/etc/init lang=us keyboard=es xkeyboard=es screen=800x600 floppyconfig apm=power-off hda=scsi hdb=scsi hdc=scsi hdd=scsi hde=scsi hdf=scsi hdg=scsi hdh=scsi vga=791 initrd=miniroot.gz nomce quiet BOOT_IMAGE=knoppix
LABEL knoppix-txt
KERNEL vmlinuz
APPEND ramdisk_size=100000 init=/etc/init lang=us keyboard=es xkeyboard=es screen=800x600 floppyconfig apm=power-off hda=scsi hdb=scsi hdc=scsi hdd=scsi hde=scsi hdf=scsi hdg=scsi hdh=scsi vga=normal initrd=miniroot.gz nomce quiet BOOT_IMAGE=knoppix
LABEL expert