Searching is possible when creating a recipe or by searching the Ingredient Center.
In each place, there is a gearwheel icon. Click this to select which catalogues to search.
To change the number of Search items returned, go to My Preferences, then select 10, 20, 30, 40 or 50 from the 'Number of search results shown per page' dropdown.
When the first (eg) 50 are shown, it is possible to extend that list with more Search results (if there are any) by clicking More Results.