How to test the existence of a property in a custom query in a custom property on a device in Logicmonitor?

As far as I recall, you cannot define a dynamic group using inherited properties.  We have had to do contortions to get around that restriction as well.  You might be forced to create a propertysource that assigns auto.XX properties and then use that to define the dynamic group.  I am not sure why this restriction exists, never have received a satisfactory answer.