Being able to do this from a right click on the host page would best the best. Half our techs want to connect to host first half want to go directly to backstage. Ex. right click has option for Join console and Join Backstage

Anyone that is still waiting for this. I have found a way to do this monthly.

Session Group: Offline Workstations since 4.11.17 

Session filter: (GuestConnectedCount = '0') 

Subgroup Expression: IIF (GuestInfoUpdateTime > '4/11/2017', '< 30days', '> 30days')

I just change the name and date in the subgroup expression and it will show machines that have not connected in  > and < 30 days.