With so many units to view, it can become a bit overwhelming showing all of them at once. For that reason nothing like a filter to be able to see only the ones you are really interested in! Here comes the Favourite Filter! To select your favourites, just swipe on a unit/category click on the Star and that is it! Your favourite is active and you will see it once you filter.
To filter, just click on the star at the top right-hand side of the screen (in both category and unit view).