A project without any associated releases, or a release associated with a given project, are equivalent to a "context".
A context determines the models and data being worked with, allowing you to easily switch between the projects and releases you are editing in Test Modeller.
All projects and releases appear in the "Project and Releases" tab; however, only the files for a given project or release will appear in the "Test Insight" and "Test Modeller" tabs when a given context is selected. All files appear when "Global" is selected.
A drop-down menu next to the Test Modeller logo navigates between contexts: