To define a reference field referring to active users, select Users in the reference field configuration dialog box.

To define a reference field referring to projects (of specific categories, for which the users have specific permissions), select Projectsin the reference field configuration dialog box. For example, reference to projects of the Scrum category for which the current user has project administrator permission:

If you do not specify a project category, projects of any category match. If you do not select any project permissions, all projects that are visible to the current user match.