You can search for specific songs from any screen where the search field is available by tapping/clicking on it.
Songs can be searched by artist or title. Simply start writing your search criteria in the field and the results refresh automatically based on what you wrote. If you'd like to add filters to your search, simply tap/click on Filters in the top right hand corner.
You can then add filters by tapping on the numbered difficulty levels you want to search for. If filters are used, you do not need to add anything to the search bar but will automatically be presented with every song for the level range you chose.
Clicking the back arrow will reset the search and tapping on the Filter icon will hide the levels. If you want to change the search filters, you can do so by clicking/tapping on the numbered difficulty levels.