...
In this case, we will create a project custom field called: Country. Please, keep in mind that there will be no need to add it to a Layout).
Configure Elements Connect
In order to configure Elements Connect properly, please follow these steps that Elements has kindly shared with us: https://doc.elements-apps.com/elements-connect/6.0/jira-administrators/configuration/field-configuration and create a custom field.
Once the previous steps are done you would only need to indicate the parameters, using our our REST API service, that will allow us to get and use the before mentioned values.
Configuration example (158 is the Projectrak field ID previously created.)
Result
Using Projectrak and Elements Connect, you will be able to provide your team with one or many custom fields which values would be able to be defined by Projectrak admins, taking a big workload from the Jira Admins shoulders. 
...