Antonello,

Do you mean the dialogbox if you use the alert() function? Then the answer is no, but if you use the dialog() function the answer is Yes.
You can use html in a dialog() function and here the dialogbox is dimentionable (but limited).

e.g. use this code in a button to display a sort of alertbox:

let h := " <h3 style='color:blue;'>This is a heading</h3>
<hr>
<ul>
<li>List Item 1</li>
<li>List Item 2</li>
<li>List Item 3</li>
</ul>
<p> Paragraph text </p>";
let result := dialog("Pick a code: ", h, ["OK"]);
if result = "OK" then void end

then you get this:

Steven