For me it seems like the diff-ext-setup needs to have privileged right. It then stores the settings for the administrator elevated user. But using the standard user when using it, it can't read the settings it wrote using the administrator. Running diff-ext-setup as administrator shows the right settings. But running it as standard user, it seems not to save the settings, so the settings are empty when running the setup again. So I guess it is not possible to use diff-ext using Windows 10 and Windows...