Thanks, I didn't realise that Host was discontinued! I have just checked for updates and happily registered that "Repetier-Host Mac 1.2.1 is currently the newest version available."
I will look into Server.
Workaround for changing settings is to edit the ini-files. I did that yesterday, but didn't see that finder was hiding the extension. So my new .ini-file was in reality a .ini-copy-file and therefore not recognised by Slic3r.