In case you are selling controversial or sensitive items and do not want to promote them, it is easy to blacklist unwanted items from recommendations on Nosto Admin Panel. Alternatively the availability detail for such products can be mapped as out-of-stock, which automatically removes the products from Nosto’s recommendations: a built-in feature.
Therefore if you want to blacklist entire product categories from Nosto it is easiest to mark such products as being out of stock in implementation. This will then mean that Nosto will index and track browsing patterns and conversions accordingly, but would never recommend in any use case products that are reported as out-of-stock/unavailable.
More typical and supported scenario is to filter results i.e. recommended products in different use cases to support specific desired business goal and user experience. For example, since Nosto creates and delivers recommendations defined by customer behaviour, we can’t exclusively prevent recommending products for female when viewing a product for men unless the gender detail is reported for Nosto and results narrowed down to support the intended purpose.
Manual merchandising is not currently supported as usually e-commerce platforms include features for promoting specific products, so we’d suggest you use promotive tools instead and Nosto as an automatic tool when hand-picking recommended products is not desirable.