Customizing Nginx (settings)

I have configured OMV 4 to force SSL usage and I'm running Baikal for syncing calendars to some Android 4.2/4.4 smartphones. Those old Android versions don't work with the default ssl_ciphers, so I have to add additional ones to /etc/nginx/openmediavault-webgui.d/security.conf.

In addition to this I'm running some PHP services and I have setup the paths and usage as described there. To make this working another include directive has to be added to /usr/share/openmediavault/mkconf/nginx.d/10webgui.

With every update, my manual additions are being deleted, so I'd like to know if there is any way to customize Nginx to allow such customization?

Thanks for the hint. From poking around in https://wiki.openmediavault.or…Environment_Variables/all I expect that OMV_NGINX_SITE_WEBGUI_INCLUDE_DIR and OMV_NGINX_SITE_WEBGUI_SSL_CIPHERS are the ones that are relevant for me and I have to set them in /etc/default/openmediavault, correct?
But will they be appended to the defaults or will they overwrite the defaults?