Portfolio category filters

Hello,

I am working with 4 categories (within each sit 4/5 sub categories). I would like to show a single portfolio across all categories. This works fine by using the “category=” code and separating each parent category by a comma.

The question I have is about layout, as I end up with some 20 filters at the top of my portfolio: is it possible to group them by main category by any chance?

Many thanks