How can we filter an object property by 'is null' and another string value?

[StaresAtSun]

I do not see a way in the Workshop UI to perform a compound filter on ‘is null’ + another property value, like a string. Is there something I’m missing before I use code to perform the filter?

[StaresAtSun]

Resolved by creating a separate object set variable with the string filter, and performing a union with the is null.