Different parent Proxys

[AC]

Hey Folks!

I'm planning to use Opnsense as Firewall, but i got a little bit stuck in the Proxy section.

I need to use a special parent proxy, but only for a few URL's. Im familiar with Sophos UTM and there is a possiblity to configure that in their GUI. I searched the Forum and found that https://forum.opnsense.org/index.php?topic=3345.0
It seems like the entries are made directly to the squid.conf which states "Do not edit this file manually".

So... any suggestions where to add the entries for the parent proxie?