I found a small solution BUT its not the best instead of what you ask!
You can create an custom page template in your theme or child theme https://www.wpbeginner.com/wp-themes/how-to-create-a-custom-page-in-wordpress/#manual
And paste the code:
https://www.w3schools.com/howto/howto_js_alert.asp
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
.alert {
padding: 20px;
background-color: #f44336;
color: white;
}
.closebtn {
margin-left: 15px;
color: white;
font-weight: bold;
float: right;
font-size: 22px;
line-height: 20px;
cursor: pointer;
transition: 0.3s;
}
.closebtn:hover {
color: black;
}
</style>
</head>
<body>
<h2>Alert Messages</h2>
<p>Click on the "x" symbol to close the alert message.</p>
<div class="alert">
<span class="closebtn" onclick="this.parentElement.style.display='none';">×</span>
<strong>Danger!</strong> Indicates a dangerous or potentially negative action.
</div>
</body>
</html>