You can use the following Javascript in "Userview Builder > Settings > Custom Javascript" and change the favicon_my.ico image filename accordingly.
Then copy your .ico image into "...\apache-tomcat-8.5.23\webapps\jw\images\" folder.
Code
// Set the Favicon as the page is loading
$("#favicon").attr("href","/jw/images/favicon_my.ico");
$(document).ready(function() {
// Set the Favicon after page load, in case the above doesn't set it properly
$("head").append('<link rel="shortcut icon" href="/jw/images/favicon_my.ico"/>');
// This might be required as well in some browsers
$('link[rel="shortcut icon"]').attr('href','/jw/images/favicon_my.ico');
});
Credit: Solnet Solutions