In admin I want to add product category filter in order grid so that admin can filter by category and processed the order. Please help me guys. Thanks
As per your requirement it is very lengthy process we need to load every ordered items and get category for all of items for all orders.
so it will cause page speed issue.
but you can add filter by SKU.
to add filter by sku you can follow below answer which is used to add skus column to sales order grid then you can add filter for that also by modifying ui_component xml file.
Hope this solution help you to complete you task.