if you want to change what's in the panel, look at the file -
/etc/skel/.kde/share/config/kickerrc

to start kde -
after you chroot -
mkdir /home/knoppix
cp -r /etc/skel/* /home/knoppix/
chown -R knoppix:knoppix /home/knoppix

on a different terminal (not chrooted) -
Xnest -ac :1

back to chrooted terminal -
export DISPLAY=localhost:1
su knoppix
startkde

when you're done, copy /home/knoppix back to /etc/skel, and remove it.