ENvironment variables into dashboards

Good morning there,
it is possible to pass a custom environment variable into a dashboard?
Specifically, I’m using the AJAX plugin and I want that the url that is used for the AJAX call to be filled with my server domain.
My dashboard is provisioned through a local json file but I don’t know how to make that the url field of the json file become filled with the domain of the server dinamically, so I don’t need to worry when using the dashboard in different servers.
(I already have the value of the domain into an environment variable.)
Thank you very much! :smiley: