It seems that 3 items are forced : Browser, Chess and Tweak Settings.
For your personnal commands, you can prefix them by a number.
I did it, it works well : (names of commands are in French ... me too
[CustomCommands]
1-Veille=tweaks.sleep()
2-Eteindre=tweaks.powerOff()
3-Redémarrer=tweaks.executeSystemCmd(\"/bin/busybox reboot\")
4-Récompenses=tweaks.readingLife()
5-WiFi=tweaks.connectWifi()