You can do it using UNUserNotificationCenter & UNNotificationContentExtension protocol
Add action using UNUserNotificationCenter
let center = UNUserNotificationCenter.current()
center.delegate = self  
center.requestAuthorization (options: [.alert, .sound]) {(_, _) in 
}  
let clearAction = UNNotificationAction(identifier: "ClearNotif", title: "Clear", options: [])
let category = UNNotificationCategory(identifier: "ClearNotifCategory", actions: [clearAction], intentIdentifiers: [], options: [])
 center.setNotificationCategories([category])
Add a delegate method of the protocol UNNotificationContentExtension in your extension's view controller
 func didReceive(_ response: UNNotificationResponse, completionHandler completion: @escaping (UNNotificationContentExtensionResponseOption) -> Void) {
    if response.actionIdentifier == "ClearNotif" {
        UNUserNotificationCenter.current().removeAllPendingNotificationRequests()
        UNUserNotificationCenter.current().removeAllDeliveredNotifications()
    }
    completion(.dismiss)
}
Try it and let me know it works.