How to convert a category into an attribute

Hi,

I asked a question here yesterday https://xtemos.com/forums/topic/how-to-create-a-new-page-for-a-group-of-products/ . I indeed created more categories for the sub menu products of my mega menu. But new problems have come. The filter is now displaying all the categories because it is Woo commerce categories, whereas I only want to display the main menu not the sub menu items.

I want to delete those categories related to the submenu items, and designate attributes instead of categories to these sub menu items. But, how to maintain the same product grid style when the links are created under attributes? Because previously you said when designate them as categories, they will inherit the same grid style.