ProxyFire by Diego Fernando

This add-on allows to proxy each of firefox containers individually also it add the custom X-Fire header with the name and color of the container that generates the request so if can be highlighted/filter in the proxy app you a re using

Also it has a short list (that can be modified from the add-on settings) of hosts (telemetry, etc) that should not be sent to the proxy (generating less garbage) but the request won't be blocked. To enable this feature just select the corresponding checkbox