Newer versions of the NetworkManager require the CA private key to connect to
the OpenVPN network. Without CA private key the settings can't be saved. I am
pretty sure that most OpenVPN providers don't share their private key for their
CA and this basically blocks setting up an OpenVPN connection.

The same bug was reported for Arch Linux a few weeks ago:
https://bugs.archlinux.org/task/59677

Their solution was to downgrade the nm-connection-editor to an earlier version
that didn't require the CA private key.

Information for package NetworkManager-openvpn:
-----------------------------------------------
Repository     : openSUSE:Tumbleweed                   
Name           : NetworkManager-openvpn                
Version        : 1.8.4-1.2                             
Arch           : x86_64                                
Vendor         : openSUSE                              
Installed Size : 155.9 KiB                             
Installed      : Yes                                   
Status         : up-to-date                            
Source package : NetworkManager-openvpn-1.8.4-1.2.src  
Summary        : NetworkManager VPN support for OpenVPN

Information for package NetworkManager:
---------------------------------------
Repository     : openSUSE:Tumbleweed                       
Name           : NetworkManager                            
Version        : 1.12.2-1.2                                
Arch           : x86_64                                    
Vendor         : openSUSE                                  
Installed Size : 5.2 MiB                                   
Installed      : Yes                                       
Status         : up-to-date                                
Source package : NetworkManager-1.12.2-1.2.src             
Summary        : Network Link Manager and User Applications