You must follow the steps below in Salesforce Classic.
To Configure Business Object Field
Go to Setup > App Setup > Create > Objects and select Search Filter (CPQ).
Select Business Object under the Custom Fields & Relationships section.
From Values section, Remove SearchAttributeValue__c by clicking Del. This value must be deleted if it has not already been deleted.
Click New to add the following values in the picklist. Enter the API names of the objects you want to be able to use as a filter in separate lines. For example,
To define visibility for products add the following values.
Apttus_Config2__SearchAttributeValue__c
Asset
Apttus_Config2__AssetLineItem__c
Product2
To define visibility for categories add the following value.
Apttus_Config2__ClassificationHierarchy__c
Click Save.
To Configure Filter Type Field
Go to Setup > App Setup > Create > Objects and select Search Filter (CPQ).
Select Filter Type under the Custom Fields & Relationships section.
In the Values section, click New and enter the names you want to use to group the Business Object picklist values.
For Products
Asset
Product
For Category
Category
Click Save.
From Field Dependencies section, click New.
Select Filter Type from Controlling Field drop-down and select Business Object from Dependent Field drop-down.
Click Continue.
Select which business object fields should be associated with which filter. To select the Business Object value, double-click the value.
Click Save.
The settings have now been configured so that you can create Search Filters (CPQ).