Azure DevOps boards styles - Parent field empty

[hellomyname490]

We аre trying to implement items on a board in Azure DevOps which are colored in case they have no "Parent" associated with them. Currently, we are struggling with the correct value clause here.

We have tried different things like "does not contain" "*" or "[Any]" however this is not working. What would be the correct Operator and Value we need to use here?

[#2]

I was just trying to get this functionality to work.

I think I have something that does what I want to highlight tickets with `No parent`. My Rule criteria looks like this:

Parent < 0

It seems to work.