Privoxy working properly with Firefox but not Chrime (linux mint 18.3)

Searching the internet I do not find any reasonable clues about
google-chrome proxy settings.

I made system wide settings (using the network manager) and Firefox worked
properly.
Chrome - not so much. Found all sorts of out of date settings advice.
Also advice setting the environment variable. No help there at all either.

Went to down and dirty editing the command line. Opened
/usr/share/applications/google-chrome.desktop and added proxy to the
command. Still no success. But I found that if I open an incognito window
chrome DOES use the proxy setting.

Now I know that modification of the
/usr/share/applications/google-chrome.desktop is not the correct way to set
the proxy.
I just have not been able to find the proper way since google went to the
gui settings interface.

Any suggestion??

Thanks
Tom Stephenson