[cgroth]

Windows OpenVPN client.

That's the client you'll need. When you set up the server on the Synology (I think I gave you some reference links for that before?) you can export a configuration file from it for the client. You just need to download the client and install it, then link that configuration file to it and it should allow you to connect the cabin PC into your home network remotely. Then all your normal connection methods (SMB, NFS etc) should work in exactly the same way as if you were at home.

This kind of VPN call back home is one of the legitimate uses for VPNs in relation to Kodi, but as noted before as it is outside of Kodi it's not something we really officially support in detail. But there are OpenVPN forums that can give you help if needed.

Hi Darren, I think I may successfully have set up the VPN, but I cannot tell if this is the case. Apart from an icon on my desktop and notification tray, which I have clicked and apparently successfully logged in with, I see no differences on my PC, including when looking for the NAS under Network using Windows Explorer. I realise that VPN is not supported by the KODI forum, so this is just information for someone else trying to use KODI to access their own NAS in a legal way:
I don't find the NAS using the Windows Network (SMB) alternative under "Browse for new share". I also tried Add Network Location, but cannot see anything. I have looked at the VPN forum and understand very little of what is said there. I like watching movies, but I have no IT expertise. I am very grateful for your tips and patience, but as I feared this is just much too complex for me.