Set category thumbnail without setting category image

[Kozlo]

Hi all, I have a question, in my shop I removed the category image using css because I don't need it, but I face a problem with category thumbnail image.

 

I can't set the thumbnail of the categories or subcategories without placing the category image (even if it is not displayed). My question is, how can I fix that? Because right now I have to place both images and it's kinda useless because category image is not used. So I want to set the thumbnail image, without setting category image and this have to be displayed on the site.

 

Does someone have some idea how to achieve that?

 

Thank you all.

 

Regards