When I take a look at the demo of the theme Beta I see in the desktop version when you click on a category a sidebar with the subcategories to filter on.
Only on a tablet portrait and mobile version of the theme you don't see these subcategories when you open a category page.

There is a filter button at the bottom of the screen to filter only there are no subcategories inside this filter.
Would it be possible to also add these subcategories inside the filter page on a mobile device?

@vansebas
Tablet -> categories in sidebar
Mobile -> categories can be invoked by clicking on filter button > category selection