Using wpa with a usb wlan stick. Configured for first wpa network with yast.
Adding a second configuration with a text editor for a second wpa secured
network fails. 
It is possible to add additional params in the
/etc/syconfig/network/ifcfg-wlan-usb file in the form _1
these params get into the resulting /var/run/wpa_supplicant-wlan0.conf file
for the wpa-supplicant.
The parameter WIRELESS_WPA_PSK_1 from /etc/sysconfig/network get lost while the
script /etc/sysconfig/network/scripts/ipup-wireless generates the needed
wpa-supplicant configuration in  /var/run when you use the command ipup wlan0 to
activate the network.
What you get from that script are two network blocks in
/var/run/wpa_supplicant-wlan0.conf, all params (as far as I use them) getting
correct in multiple network blocks as needed. (Even for more than two of them)
But the only params that does not work are the WIRELESS_WPA_PSK and
WIRELESS_WPA_PSK_1. You get in the first network block the correct entry for the
value of WIRELESS_WPA_PSK and in the second network block the same value of
WIRELESS_WPA_PSK added a "_1" and not the value of WIRELESS_WPA_PSK_1.
Same for a third definition _2 you get the value of WIRELESS_WPA_PSK added a "_2".

Example for resulting wpa_supplicant-wlan0.conf file:

ctrl_interface=/var/run/wpa_supplicant
network={
  scan_ssid=1
  ssid="ssidnumberone"
  key_mgmt=WPA-PSK
  psk="mysecretpassword"
}
network={
  scan_ssid=1
  ssid="ssidnumbertwo"
  key_mgmt=WPA-PSK
  psk="mysecretpassword_1"
}
network={
  scan_ssid=1
  ssid="ssidnumberthree"
  key_mgmt=WPA-PSK
  psk="mysecretpassword_2"
}
tried to debug the /etc/sysconfig/network/scripts/ipup-wireless script, but
sorry that is beyond my knowledge of shell programming.

Greetings
Andreas