Maybe I am really blind, but customizing the toolbar/searchbar in dolphin didnt end with the proper result: I only found either a search button which invokes a filterpane or another button that reveals a search bar below.

What I am looking for is to have a searchfield always visible like the one next to "Preview" in this screenshot:

This was present in an older version but was replaced with the current implementation (search with Ctrl+F or click the search button).