The issue should be applied to CM and CQB.
There is an option to set "NULL" data for Data import. Users should click <file>/<default setting>/<Data import Option>
1) It is hard to find the NULL data related option when Data importing. The option setting UI should be merged in Data importing UI menu.
2) CM and CQB only supports "NULL" data option only for Data import. It is necessary when users exporting data from the DB. The same option should be in Data export UI.
Data import/export is a feature so useful to users. The feature/UI should consider user experience.