I came up with a fix, and it will be included in the next release.
I just released the latest version on the weekend, so it may be weeks or even months until the next update.
But it is actually fairly easy if you want to integrate it yourself.
Open include\staff\tasks.inc.php and change line 286 from
<!-- SEARCH FORM START -->
<div id='basic_search'>
<!--osta-->
to
<!-- SEARCH FORM START -->
<div id='basic_search'>
<div class="pull-right" style="height:25px">
<span class="valign-helper"></span>
<?php
require STAFFINC_DIR.'templates/tasks-queue-sort.tmpl.php';
?>
</div>
That will return a fully functional Sort button to the page. But it will be a little misaligned.
For good measure, you can add this to you Theme Options > Custom CSS:
.tasks-page #content .pull-right .action-button.muted, .action-button.muted[data-dropdown="#sort-dropdown"] {
top: 4px;
right: -8px;
margin: 0;
}
Let me know if you have any trouble with these instructions.