You need to create a derived property before you can add a direct category or a characteristic to your search properties.

That means that you need to make the characteristic price available as a property if you want to use, for example, the Group derived property. It would be best if the price is used as a property in your feed, so that it can be found in the module Catalog > Feed properties. This causes the price to occur twice in your feed, as a property, and as a characteristic.

Navigate to Catalog > Derived properties and click +New. Select the Advanced type. Here, you can create a property based on an SQL query.

First, name the property. Choose for a name that contains direct category to keep it clear. The Property URL name is generated automatically, so you may leave this field empty. In the Select a SQL query field, you can construct the query using the buttons, or you can paste in this query:

[Categorie].Naam as waarde,
1 as volgorde

NOTE: It's currently impossible for us to make English subqueries available. As you can see, they are in Dutch. For your convenience, we've added English buttons. Quick translation of the subqueries:

• Categorie = Category
• Naam = Name
• waarde = value
• volgorde = order

Next, Save the derived property. You've made a Direct category derived property! Click the Preview tab to see how it's been filled. Don't forget to add the new property to your Search properties (Search > Search properties).