hi
try to use opnsense_stream_vhost_plugins folder for the file with your custom config
https://github.com/opnsense/plugins/blob/3c5e2b9d771bf8e7145eb659f1d8a4302640cc62/www/nginx/src/opnsense/service/templates/OPNsense/Nginx/http.conf#L69C1-L69C18
try to use opnsense_stream_vhost_plugins folder for the file with your custom config
https://github.com/opnsense/plugins/blob/3c5e2b9d771bf8e7145eb659f1d8a4302640cc62/www/nginx/src/opnsense/service/templates/OPNsense/Nginx/http.conf#L69C1-L69C18