If you do not plan to access any of the data within a specific survey, and would like to remove it from your dashboard, you have the option to archive it.
To archive your survey, click on the "Options" button next to the survey name, and click on "Archive" from the drop down.
Once you archive a survey, it's moved to a separate tab on your dashboard. Even though they are archived, you can still view the content, targeting, and responses from each survey.
If you still need to export the responses, clone the survey, or otherwise make any changes to it, you will need to move the survey back to your dashboard. Archiving a survey is a lot like a soft delete, so make sure to only move surveys to this area when you're finished with them completely.