The server list is an auto-fill helper to fill type, hostname and port. Extensions do not have direct access to other applications running on users computer.
PAC don't work :( (Sorry previously wrote UAC, my bad) Example on Reddit thread 18i3gtc or search "foxyproxy Android pac" or in my case p.thenewone.lol:8443/proxy.pac
See discussion at https://github.com/foxyproxy/browser-extension/issues/177 and please check the included Help under "Pattern Guide" and post to the support if needed.
