Hello martinvox,
It is described here:
https://openvpn.net/vpn-server-resources/managing-user-and-group-properties-from-command-line/#redirect-gateway-and-dns-settings
In particular this bit:
Redirect internet traffic for a user, but don't push DNS servers:
./sacli --user <USER_NAME> --key "type" --value "user_compile" UserPropPut
./sacli --user <USER_NAME> --key "access_to.0" --value "+NAT:0.0.0.0/1" UserPropPut
./sacli --user <USER_NAME> --key "access_to.1" --value "+NAT:128.0.0.0/1" UserPropPut
Redirect internet traffic for a group, but don't push DNS servers:
./sacli --user <GROUP_NAME> --key "access_to.0" --value "+SUBNET:0.0.0.0/1" UserPropPut
./sacli --user <GROUP_NAME> --key "access_to.1" --value "+SUBNET:128.0.0.0/1" UserPropPut
Please read the document for more information.
Kind regards,
Johan