By holding Ctrl you can select multiple replay files and render them as a queue, which is quite handy.

There is an asymmetry though, when selecting a single file, you don't have the option to render its queue, you have to load the world and do it from the inside.

I can't see why a selection of 1 file is any different from a selection of more. Being able to render from the replay viewer and not having to load the world is convenient if not powerful.