I'm using Mac Catalyst to port an iPad app to Mac. I'm able to create multiple windows using:
func requestSceneSessionActivation(_ sceneSession: UISceneSession?, userActivity: NSUserActivity?, options: UIScene.ActivationRequestOptions?, errorHandler: ((Error) -> Void)? = nil)
Also, I'm able to arrange the created windows in tab from the application's menu:
Application Menu > Window > Merge All Windows
But I don't see an option to programmatically do so. I would use NSWindowTabGroup in AppKit. However, it is not available in Mac Catalyst. Please let me know if it is possible yet?