Sorry @escalade that I did not go your way at first. I couldn't find an easy way to realize it (no experience at all for this), but instead I had the templates for systemd services in LibreELECs .config folder. Your solution sounds kind of perfect in terms of flexibility, when reading it now after you explained it a bit further
Do you think that it would also be possible to take user defined into account? I'm using PureVPN, but I'm using custom *.ovpn files for it with your User Defined option, because this way I can specify also direct connections to the Servers IP-addresses behind their DNS names.
Corresponding IP-Adresses after resolution: 22.214.171.124 and 126.96.36.199 and 188.8.131.52 etc.
Doing this method, because sometimes the servers are overloaded and slow and then I can cherry pick them by choosing different *.ovpn's to find a server that is kind of less used at the moment.