Question VPN Module for site-to-site connection

[southy]

Dear everybody,

The VPN module in Plesk requires me to enter local & remote peer address for a VPN connection.
However what I want to do is not a machine-to-machine connection, but a site-to-site connection [or at least (Plesk-)machine-to-site].

It appears the Plesk VPN module GUI is just suited to create machine-to-machine connections, as it will not accept e.g. 10.0.0.0/16 as local or remote peer addresses.

That's unfortunate, as I aim to replace an existing machine (no plesk), where the tunnel ends in a Strongswan, which this is pretty easily defined in strongswan.conf:

conn xxxxxx
        dpdaction = restart
        left = 51.??.??.??
#       authby = psk
        leftcert = vpnHostCert.der
        leftid = siteconnect.xxxxx.xxx
        leftsubnet = 10.41.0.0/16

        right = 217.??.??.??
        rightid = name
        auto = start
        authby = psk
        keyexchange = ikev1
        rightsubnet = 10.41.0.0/16

Note that in strongswan, by setting "leftsubnet / rightsubnet", I define a site-to-stite connection.
Would I use "left / right" and set a IP instead of a network address, it would be a machine-to-machine connection.

How can I achieve this in Plesk?
Can I manually set this in a config file or via CLI, as it doesn't seem to work via GUI?

Apparently, the config files should be located in /usr/local/psa/var/modules/vpn/
However, there's no config file here; just a key file "vpn-key".

EDIT:
Oh, I see: the config files is only present when the connection has been activated - once it is deactivated, config files vanish. Well, so much about that.
Still leaves the question open on how to configure this in GUI - or if it's a good idea to manually change config files...

Has anyone and idea on how to do this?