I think this can be done using BugMonkey. For instance have a look at this script.
Update: I edited the script to have the icon inserted in a place visible for all users:
name: Reverse BugEvents
description: Temporarily switches BugEvent order
author: Tyler Hicks-Wright, Michel de Ruiter
version: 1.1.0.0
js:
var be = $('#BugEvents');
if (be.length > 0) {
var wher = '.statusbar';
if ($(wher).length == 0) {
wher = '#statusbarspacer';
}
$('<a>').appendTo(wher).addClass('TGHW_BugEventOrder')
.attr('href', 'javascript:void(0);').attr('title', 'Reverse events')
.click(function() {
$('#BugEvents .bugevent, #BugEvents .pseudobugevent')
.each(function(i, e) { be.prepend($(e).remove()); });
});
}
css:
.TGHW_BugEventOrder {
background: url(http://tghwmedia.appspot.com/media/hwnet/img/ui-accordion.png) no-repeat;
height: 16px;
width: 16px;
display: block;
float: right;
}