addNotification.js

phoneNotification: function (executionContext) {
    let formContext = executionContext.getFormContext();

    var phoneControl = formContext.getControl("telephone1");
    var phoneNumber = formContext.getAttribute("telephone1").getValue();
    var notification = {
        messages: ["Copy phone number"],
        notificationLevel: "RECOMMENDATION",
        uniqueId: "phone_notification",
        actions: [{
            message: "Copy",
            actions: [function () {
                navigator.clipboard.writeText(phoneNumber);
                phoneControl.clearNotification("phone_notification");
            }]
        }]
    };
    phoneControl.addNotification(notification);
}