What must be true when "Use Expressions" checkbox is set to True in a saved search?

When the "Use Expressions" checkbox is set to True in a saved search, it indicates that more complex expressions can be utilized in defining the search criteria. This allows users to create logical combinations of filters that can involve multiple fields and more intricate conditions.

In this context, having a filter that does not use the same field as the Criteria is essential. It ensures that the saved search can properly utilize expressions without leading to ambiguity or conflict between the filters and the criteria itself. By avoiding the use of the same field in both places, it allows for a clearer structure in how the logic is applied, enabling robust and flexible query definitions.

The other options are not inherently required when "Use Expressions" is enabled. Specifically, there is no need for every line to have parentheses, a numeric field is not obligatory, and filters do not have to be optional for the search to operate correctly. Therefore, the requirement for a filter to not use the same field as the Criteria aligns with the functionality that the "Use Expressions" feature is designed to facilitate.