Remove pictures with missing referenced files
I am on Big Sur. I noticed that several pictures in the Library are showing unknown reference. Probably I deleted them from the hard drive but they are still in the Photos Library.
How do I delete these pictures with missing referenced files? In previous versions of Photos there was an option to create smart albums for pictures with missing referenced files, but now this option is not available anymore.
iMac 21.5″, macOS 11.0