You need to create a separate store template or new page layout and assign only the “Kitchen Appliances” and “Computer Accessories” categories to it.
Then remove those categories from your main menu by unchecking them from the default navigation.
Most platforms (Shopify, WooCommerce, OpenCart, etc.) allow you to:
Create a new page
Assign a custom menu to that page
Display only selected categories
This will make the new page function like an independent store section.