Null values appearing in data is almost inevitable. To help users discover where data is missing, I think it would be useful to be able to make those null values searchable/selectable, per field basis.
To speed up development, and reduce conditional/replace logic, it would be useful for developers to tag fields where data should always be populated. If null values appear in those fields, Qlik Sense interprets the nulls to make them searchable/selectable by end-users, enabling them to quickly identify and explore those values, and associated data.
Currently, this can be a time-consuming exercise for both developer and end-user.