I just found that about half an hour ago, thank you . If I go through Comm > Friends I see the options Wulfie is talking about too. I wonder why they're so different, it doesn't make sense that they would be.
What's really crazy is that this "toggle friends invisibility" option has been available since 2015, yet there are loads of posts here and on Reddit asking if it's possible as recently as 2021. In every case the answer was "no, not possible, never has been" - Wulfie's reply is the first time I've seen someone show that it is!