Hello,

you can achieve it by following the steps below:
1. Log into your site as an Admin
2. Open the Administration pages
3. Navigate to the Batch Manager in the Photos section
4. In the Filter section, choose "add Filter --> Predefined Filter"
5. Use the predefined Filter "With no tag"
6. Press "Refresh Photo Set"
7. Here you are.

I have also installed and activated the plugin "Batch Manager Prefilters". I think that this one is needed.

Best regards

Jens