CPQ enables you to create a Cart in which your Sales rep can just view the product configurations and not make any changes to the field values for the Product Line Items. In order to achieve this functionality, you must specify a new parameter mode=readOnly while creating a custom button to launch the New UI.

IF ( LEN( Apttus_QPConfig__PriceListId__c ) > 0 ,HYPERLINK("/apex/Apttus_QPConfig__ProposalConfiguration?id=" &Id& "&flow=ngFlow"&"&mode=readOnly",IMAGE("/resource/Apttus_QPConfig__Button_Configure", "Configure Products"),"_self"), NULL)
CODE

By applying this formula to your Configure button, the checkboxes of products and the action buttons are disabled on the Cart page when the sales rep accesses the cart in read-only mode. This prevents your sales rep from applying any mass updates to the products in the Cart. In read-only mode, the Sales rep can still create views, search the products, and filter the line items on the cart.