Varnish reverse promxy selection by hosting client

Noob here. Is there any way for the hosting client to select varnish for their domain.
In my set up varnish is not default server set up. I understand admin has to enable varnish for domain under domain configuration.
Is there any way a end client can select Varnish reverse proxy in their client panel (@ :2083)?

No.
This is available only at root CWP panel, in Webserver Settings -> Webserver Domain conf -> select the username of your user -> Click in the button "View/Edit configuration", and choose the template of preference.