To make FiboSearch look for products in certain categories only,
go to WooCommerce →
choose the “Search config” tab. At the bottom of the config page, you’ll see the following section:
Set the Filtering mode to “Include” and then set the Filters to the categories you want to include in searches. You can also narrow searches down to products with given tags.
Save your changes and rebuild the index. From now on, FiboSearch will only search for products in selected categories.