Sadly, the easy way in connman, is to edit the file..
root@test-bbgw-12:~# cat
/var/lib/connman/wifi_209148c9516a_584131302d576946692d5831_managed_psk/settings
**************
Name=XA10-WiFi-X1
SSID=584131302d576946692d5831
Frequency=2412
Favorite=true
AutoConnect=true
Modified=2017-02-01T17:38:45.134985Z
Passphrase=BeagleBone
IPv4.method=dhcp
IPv6.method=auto
IPv6.privacy=disabled
IPv4.DHCP.LastAddress=192.168.0.2
**************
Then change the Passphrase value
root@test-bbgw-12:~# systemctl restart connman
Regards,
--
Robert Nelson
https://rcn-ee.com/