You can add one or more application instances for inclusion in the Application Links functionality. For example, you can include two Confluence sites into your suite of Application Links applications.
Application Links supports the following applications:
For each of the above applications, you can add zero, one or more instances to the Application Links suite.
If you add two or more instances of the same application (such as two Confluence sites), then you will need to choose the primary instance. See Specifying a Primary Application Instance.
Screenshot: More than one Confluence instance in the Application Links suite
Application Links Administration Guide