Hi there. :)

Can someone explain to me why I can't go through the presets by clicking the arrows? They´re greyed out.

(Latest version here with Logic Pro X 10.5)

Cheers, and thanks in advance!

The preset browser lists all presets found in the folder location where you last opened a preset. Just click the preset display and "Browse presets...", navigate to a folder with presets and open one. You will now be able to step through all presets that are in the same folder.