The idea of having shared, that is global, elements is fine. However, I don't see that working with defining such elements withing a specific instance of the tracker module. What happens if that instance is removed? Are the shared elements gone from other instances? What about editing the shared elements in instances that use them? I think it would be a better approach to add a settings option for this module in the site administration and convert the concept of shared elements to global elements, that is elements available for any instance of the tracker but editable only by the Moodle administrators.