Same problem here. Apple, please fix ASAP!

I am struggling with this as well! It seems to be possible to add custom items on iOS using UIMenuController.shared.menuItems = [myCustomMenuItem], but when running this on Catalyst, the item doesn't appear in the text view's context menu. There's also the new func textView(_ textView: UITextView, editMenuForTextIn range: NSRange, suggestedActions: [UIMenuElement]) -> UIMenu? that suggests customizability but this also doesn't do anything for me on Catalyst. Has anyone found a solution for this?