if you go filter > lights, c4d lights will be hidden from the viewport but corona lights will remain in the viewport.
Is there another way to hide them from the viewport?
sure, but having 80 or 100 lights in the scene can be a pain to switch all on and off. using the filter is an excellent way to show them while tweaking lights and hiding when done
This. I always put my corona lights into their own null so I can toggle the whole system on or off as needed. It would be awesome if the C4D filter>Lights worked with Corona lights too,but I understand why they do not.