See: https://wiki.jenkins-ci.org/display/JENKINS/Config+File+Provider+Plugin

I have set up a generic file via this plugin, but I cannot use it because in the job I cannot pick the entries from this plugin (understandable because you don't support it).

Unfortunately, I cannot rely on the fallback behavior of copying the config locally to the job and using that file explicitly because this plugin does not allow me to enter in a specific path... it only allows me to choose from a dropdown.

We cannot allow everyone access to the master jenkins config, so forcing people to use that to configure this plugin is not really acceptable.