Is there an easy, foolproof method for copying a file from openhabianpi to a windows pc?
the openHABian installation includes the setup of some samba shared folders. If you connect to those network Folders you can handle those with the Windows (File) Explorer.
Scp or sftp should be able to work also.
Google them, lots of help.
Bitvise is my favorite for working with the PI. Offers ssh and ftp at the same time on 2 different windows, which open automatically.
Maybe you want to take a look at WinSCP which “is an open source free SFTP client, FTP client, WebDAV client, S3 client and SCP client for Windows.” The graphical user interface looks like this: