Plan: Group by custom attribute "Scheduled In"
One answer
I do not know, if your request is achievable, but if you want to use custom attributes in the classic plans, you need to create an attribute mapping for the custom attribute. This can only be done in the EWM Eclipse Client.
Open the project area (right click on the PA in the Team Artifacts view), switch to the Process Configuration tab.
Open Configuration>Project Configuration>Configuration Data>Planning>Plan Attributes
Add the custom attribute in Attribute Mapping using Add, select the custom attribute and save.
Once you have done that, you can try if you can group by the custom attribute. I do not know if that is possible. I remember there were several limitations.