We have had clients need to specify an HTTP proxy server that our various Desktop add-ons and applications need to use when communicating with some external HTTPS resources. For example when using RemoteLaunch, the DesktopDataSync or Jira Configuration Helper tools. This article explains the process for listing a proxy server.
Normally you can install the add-ons for Chrome and Firefox directly from the browser's app store (just search for Rapise). This is the easiest option, and avoids the need to run the browsers in developer mode.