When choosing something from the library, the library window is too small, and the remaining area of the screen is unused. We do not need to see the project when working with the library. Therefore, the library should be fullscreen.
I apologize, I forgot to mention: Just resizing that area will not make much improvement. There needs to be a preview of the library items, with configurable size of the images. You could get inspiration from the Windows Explorer (large icons, smal icons, tiles etc). Music should be previewable just by hovering with the mouse.