Outlook Add-in: Is there a way to customize Send Anyway button for Microsoft Smart Alert with PromptUser mode?

Question

I'm testing out the Outlook add-in Smart Alert event that trigger when a user click send email using this tutorial: Automatically check for an attachment before a message is sent

So with the SoftBlock mode, we can customize the Don't Send button. Is there a way we can customize the Send Anyway button for PromptUser mode?

Here's what I got so far:

/**
 * Office Initializes here
 * @param {Office.InitializationReason} reason
 */
Office.initialize = function (reason) {
  console.log('Addin Loading in Send Message Menu');
};

function onMessageSendHandler(event) {
  Office.context.mailbox.item.body.getAsync(
    "text",
    { asyncContext: event },
    getBodyCallback
  );
}

function getBodyCallback(asyncResult){
  const event = asyncResult.asyncContext;
  event.completed({
    allowEvent: false,
    errorMessage: "Looks like you're missing a keyword, consider adding it",
    cancelLabel: "Okay",
    commandId: "MessageComposeSelectButton"
  });
}

// IMPORTANT: To ensure your add-in is supported in the Outlook client on Windows, remember to map the event handler name specified in the manifest to its JavaScript counterpart.
if (Office.context.platform === Office.PlatformType.PC || Office.context.platform == null) {
  Office.actions.associate("onMessageSendHandler", onMessageSendHandler);
}

I tried to create another event.completed and set allowEvent to true but that just said the Add-in finish processing my email