However, how do I get this to update according to whichever network I am connected to. I don't want to have to grant root and edit /etc/environment everytime I plug I switch home vs work networks.

I think there is a tool for this in Gnome called proxydriver. I can't see this in my package manager (equo search proxydriver or emerge --search proxydriver) though and I'm not sure if this would work with XFCE.