At the moment 12 is the maximum amount of preset folders unfortunately. I would suggest creating a new "my_preset" folder on your desktop where you can "save" presets you no longer need in Feralheart but do not want to delete
To make room in your Feralheart>> my_preset folder just export your finished presets so you can use them and move the exported preset files (images, material) to your new desktop folder

Hope that makes sense and good luck
