Let's say that we want to view specific items of a host. We type its name in the search bar and click on "Items" to go the the host items configuration page. Here, a filter is automatically set on the host name. If we need to filter on a particular application, we click on the application filter select box. However, in the windows that appears, the select group is "Discovered hosts" and the selected host is the first of the list.
By default, it should be set to the host that we have already filtered. It is quite annoying as we have hundreds of hosts and it's a pain to search for the right one. Another option would be to add a search box with autocompletion in the application filter window, which would help to find the necessary application quickly.