To Unlock the Dependency Viewer Tab, So It Updates When a New Document Is Selected

In the Dependency Viewer toolbar, make sure the lock icon is in the unlocked position.
If it is currently locked, simply click it again to unlock it. When this icon is in the unlocked position, its tooltip reads, Update dependency map when new document is selected.
Test the behavior of the unlocked icon by selecting one document in the document list, and then another.
The Dependency Viewer tab is refreshed with a new dependency map each time you select a new document.