Assume we have three columns in library view: Artists, Albüms, Title. At any time, one item from each is selected. So, listing all the titles of an artist requires pressing Ctrl+A at the albums pane. This is not very practical (especially when the library is big and you did a Ctrl+A on all artists). To avoid this impracticality, please add a filter where it says All Artists... All Albüms... All Composers..., etc. And whenever selected, selects all items in that category. So, when I want to see all the titles of an artist, instead of pressing Ctrl+A, I would just click that item (at the top) and it will list all the titles on the title pane.