The Insert Citation command allows you to search your library from within Word.
In the text box at the top, enter text to identify the reference you wish to cite. EndNote assumes an “and” between each word, and will search all fields in your records.
So the window will just show you results of your search in order to see all the references on the window you have to be able to do a search for something that every references has.
You can do a search e or a but the window is just a window to show you results of a search and does not replace the library in EndNote.