Hi martinbeaumont
Yes, you can override this logo element from T4 plugin into your template.
Kindly check if this file exists on your site or not:
/templates/ja_symphony/html/layouts/t4/element/logo.php
If not, you create this folder 'element', then download attached file >> unzip it and copy the 'logo.php' file inside to this 'element' folder of your site.
In this file, I just update the code so that the slogan will show with the logo, you can see the code in line 42:
<?php if ($site_slogan) : ?><small class="site-slogan<?php echo $logo_sm_cls; ?>"><?php echo $site_slogan; ?></small><?php endif; ?>
Then you can update style for it as you wish.
Remember to clear all caches then.