In my Cookbook database I created a Diet custom metadata field and when I want all my recipes to be properly tagged so I tried to create a Smart Group that would show me files without Diet field set or without any tags. But that doesn’t seem to be possible, I can only select “is” or “is not” and give it a value to match.
The only way to do custom-metadata-is-not-set is by creating a predicate that is All → is not which isn’t create because of repetition but also because if a new value is added to the custom metadata field the predicate breaks.
Thank you both for the clarification on where the not tagged one lives, I was looking for it under the second dropdown after selecting “Tag” instead of under “Item”.
In that case this is currently not possible but on our roadmap. The only workaround would be to use multiple conditions to exclude the values of the set (like set is not value1 and not value2 etc.).