Hi,
The way that I would do it :
Put the request-termination plugins on each route that you want to disable/enable.
And then PATCH the plugins with enabled=false (for route enabled) or enabled=true (for route disabled).
You can configure the request-termination plugins with http code and message that you want to return when you consider that a route is disabled. (cf. https://docs.konghq.com/hub/kong-inc/request-termination/)