Is there a component or way to put Search in the Edit menu in a panel, and have the search happen in the playlist view? I want something that automatically updates the file list (uie_quicksearch isn't what I want).

Pretty certain you can do what you want with quicksearch. Just set the playlist name in your preferences.

But that creates a new playlist. Is there any way to make search results appear temporarily in the current playlist?

you can use the "inline playlist search" option for quicksearch.