You may want to pick a small sce, e.g., wifi.sce and "look inside".
The procedure is the same as a tcz.
unsquashfs -d wifi /etc/sysconfig/tcedir/sce/wifi.sce
The peruse the directories under wifi/
There you will see a wifi.sh script and icon.
To repack use mksquashfs:
mksquashfs wifi wifi.sce