By scope you should understand the collection of documents that define the context of
the search and refactor operations. To control it you can use the Change scope operation, available
in the Quick Assist action set or on the Resource Hierarchy/Dependency
View toolbar. Here you can restrict the scope to the current project or to one
or multiple working sets.
The defined scope is applied to all future search and refactor operations until you alter it again. Contextual menu actions allow you to add or delete files, folders and other resources to the working set structure.