From time to time you could need to manipulate the proxy configuration at low level in windows, in my experience only when SCCM is not working properly or Outlook have troubles to synchronise.
If you need to access the proxy low level configuration, you will need to use a CMD Window as Local Administrator and use the
netsh interface and use the following:
netsh winhttp show proxy - to show the current confiuguration
netsh winhttp reset proxy - to delete the current settings
netsh winhttp set proxy