Once upon a time a list needed to be filtered on demand.
Google has many solutions, many of which involve plugins and your data to be formatted per the plugins taste.
Wait tho! Marionette already can do this with your existing collectionView.
Hidden within the Marionette code base lies a handy little method waiting to be overridden
class List extends Marionette.CollectionView
addItemView: (item, ItemView, index) ->
return unless item.shouldBeShown()
** Working Example **