I notice you're asking about "Universal USB Installer version 2001" — but there's likely a confusion with the version number.
Often allows you to keep existing files on the USB if there is enough space (depending on the format). universal usb installer version 2001
Users looking for multiple OSes on one drive often prefer YUMI or Ventoy. 0.0.1 compares to the , or I notice you're asking about "Universal USB Installer
/KNOPPIX and copy the Knoppix ISO contents there.syslinux.cfg file (created during the Linux preparation step) to add:
LABEL knoppix
KERNEL knoppix/linux
APPEND root=/dev/sda1 initrd=/knoppix/minirt.gz
LABEL dos622
COM32 chain.c32
APPEND hd0 1
Tab to select your OS.