Upon further investigation, the issue is that only the last subview added to the main view appears, although the others are there. Simply changing the order in which the subviews are added changes which subview is visible. Is this a bug in Sequoia 15.1???

I did, to remove any confusion about the error messages. The subviews are not hidden (view.hidden is false). I know they are there because I can click in an invisible view and it accepts my click and does the expected thing. I am adding the subviews with: [self addSubview:JournalView positioned:NSWindowAbove relativeTo:self]; As I said, only the last subview added is visible.

Is there anything you can tell me about this issue? Does Apple recognize it as a bug in Sequoia 15.1?

Is there anything you can tell me about this issue? Does Apple recognize it as a bug in Sequoia 15.1?