This is a Feature request to add socks support in proxy plugin, currently only http(s) and ftp protocols are supported (https://github.com/Flexget/Flexget/blob/master/flexget/plugins/operate/proxy.py)

There was an old ticket with this request at: http://flexget.com/ticket/2671

I've tried adding the socks proxy in configuration as below, but did not work.

proxy: socks5://127.0.0.1:<port>

Thanks for considering!