You can use this as a starting point:
<html>
<title>long page</title>
<body>
<div style="min-height:1500px;background-color:lightblue;">tall div</div>
<div style="background-color:pink;color:red;">bottom element</div>
</body>
</html>
If you use the following version in your browser address bar, it will display it directly (no need to save it as a file)…
data:text/html;charset=utf-8, <html><title>long page</title><body><div style="min-height:1500px;background-color:lightblue;">tall div</div><div style="background-color:pink;color:red;">bottom element</div></body>
But you can’t test the last one due to a bug in Katalon (Reminder @ThanhTo).