Search boxes on zhwp used to include language-converted completions for titles written in other scripts in completion options. This, along with the default converttitles functionality, generally obsoletes the old practise of creating "language conversion redirections" for redlink detection and search boxes.
However, this functionality is no longer working in the current version. To reproduce, type the simplified version of a phrase (e.g. 电灯), and compare its completions with its traditional version (e.g. 電燈). Ideally these two lists should be identical, or at least have many intersections. Current behavior is shown below (0 common entries):
After pasting the text, you may have to perform some dummy edit like typing a space and then tapping backspace to make the completion menu appear. HotCat displays a similar regression with its completion functionality.