Welcome to the forums @nafysbrhm!
I looked through the documentation and I did not see anything built-in to the ItemList node for hiding items. One way you could handle hiding/showing items is by adding/removing them based on whether they fit the search, and after the search adding the items that did not match the search back to the list. Another thing you could try, though it would not hide them, is using the set_item_disabled function to make the items that do not match the search selectable.
