Total Commander

It would be nice if the "Feed to Listbox" feature showed only the filename rather than the full path.

The reason is that some paths are quite long and the filename is not visible making it difficult to decide which one you want to look at.

I would envision listing the filenames and then showing the path on a mouseover or by right-clicking.

It's already possible - with "Custom Columns".

Using custom columns is a good idea but just displaying the file names there often doesn't help as many search results might have similar names. When adding the path to the custom column config it will have about the same width as the ordinary search result view.
What I use since years is my Nicepaths content plugin which offers reasonable shortened paths:
http://totalcmd.net/plugring/nicepaths.html