There's a setting in Plex which looks for changes to its folders, and refreshes your library automatically. I have that on, and I see my *arr shows/movies in Plex within a minute or two of being added.

Thanks for the response and info. Another day where I'm glad to be a FF user.

I'm a Firefox user, but doesn't Chrome allow adblockers too? Both uBlock Origin and Privacy Badger are supported extensions on Chrome.