Hi,
Is there a discount module or similar that allows you to apply discount to only certain categories and manufacturers?
Thanks
http://extensions.virtuemart.net/products/quantity-related-price-calculation-detail
or use the native discounts/unpublished categories system
https://docs.virtuemart.net/manual/products-menu/taxes-and-calculation-rules.html
https://docs.virtuemart.net/manual/general-concepts/204-tax-and-calculation-rules-overview.html
A VM tax/calculation rule can be configured to only apply discount to one or more individual categories, or to one or more manufacturers, or as GJ says, you can apply discount to certain products using a hidden category. All this is inbuilt in VM.