Clay doesn't track row history or deletions, so there's no direct undo feature to recover previous versions of your data.
If you need to test changes safely, use sandbox mode: Click Actions → Turn on sandbox mode to create a safe testing environment. You can discard changes with Reset sandbox or return to your original table with Turn off sandbox mode.
For overwritten data, you'll need to re-import or manually update the information.
We understand your frustration with the accidental data loss. Version history and undo features are under consideration for future development, as we've received multiple user requests for these capabilities.
For now, you'll need to re-import or manually update the overwritten data. To prevent similar issues in the future, consider using sandbox mode for testing changes safely before applying them to your main table.