At the moment, the CPDB doesn't work well for larger sets of participants. Selection of participants is limited to 100 and it is really tedious – borderline impossible – to handle 10.000 or more survey respondents meaningfully. To add 40.000 survey respondents, based on a specific filter, to one survey, you need hundreds of clicks and dozens of hours. It would be nice to see a functionality along the lines of: select all participants with a specific characteristic, such as survey_id, and batch-add them all to a specific survey.