Some EndNote commands (such as Search Library, Change Field, Change Text, Sort, Print, and Export) can work with just those references that are "showing" in the Library window. Here are a few examples of operations that you can do with the showing references:
Restrict the Search Library command to search only the showing references.
Add the results of a new search to the current list of references as a way to combine search results. Select Add References to move the references to a particular group.
Use the Find and Replace (Edit menu) and Change/ Move/Copy Fields (Tools menu) commands to modify the showing references.
Use the term lists’ Update List command to scan only the showing references for new terms.
Create a Subject Bibliography from the showing references.
Print or Export only the "showing" references.
One way to view a subset of references is to use the Search Library command. The Show Selected References and Hide Selected References commands in the References menu provide another convenient way for you to control which references are showing in the Library window.