Hi, vsync.
To do this you would need to customise the ‘templates/portfolio.php’ template and also the CSS for that list. Maybe even the JavaScript, I’m not sure. Doesn’t look like a simple modification to me.
Something that is simple to do and might help with your long filter names is to make the filters area wider. If you look in the ‘templates/portfolio.php‘ file on line 38 or thereabouts you’ll see a chunk of code like this:
// specify width for main container for filters to align on left side
$container_styles = "width: 90%; margin-left: 0px;";
// list the filters ?>
<div class="span-custom" style="width: 9.9%;">
You could change that (for example) to this:
// specify width for main container for filters to align on left side
$container_styles = "width: 70%; margin-left: 0px;";
// list the filters ?>
<div class="span-custom" style="width: 29.9%;">
Always keep in mind that if you modify the core theme files then when you need to update the theme your modified files may be overwritten and your modifications lost. Tweaks to CSS can be added to your Custom CSS box in Theme Options. If you feel that you need to modify CSS files consider using a custom stylesheet, if you feel that you need to modify PHP files consider creating a child theme, otherwise updating the theme may become quite difficult for you.