No, this plugin can only reencode a video source, you must select a video in the project tab, not a comp.
I usually render the comp in animation with parameters i want, reimport the render in AE then convert it to prores.
If my plugin don’t work when you try to convert a video, you probably didn’t check “allow script to write files” in the general preferences.
I’m going to do an update of the script soon, with an installer, prores 4444 support and probably an automatic pre-rendering 🙂