Summary:
The new Roadmap lacks several "Group By" options present in the legacy version, such as Theme, Objective, Business Driver, Team, Custom Hierarchy, and State.
Example:

1. GROUP BY Theme – Theme Roadmap with accordion may mitigate the need to support this but we will to understand if this is planned to be supported or we need to get user feedback if this is not planned.
2. GROUP BY Objective – It is common to want to view an Outcome or Objective based roadmaps and see the key results and work associated within the quarter. If the Objective Roadmap view is expected to be the solution to this 
3. GROUP BY Business Driver, Strategic Driver: Group may not be the end solution but it’s the only solution today since either filtering or column options are available so this becomes a parity gap.
4. GROUP BY Team – This again could be mitigated if support for multi-select teams are supported via filters and columns but this is another parity gap where there is no other option in the new roadmap view.
5. GROUP BY Custom Hierarchy (Product Model) – Could be solved by the custom hierarchy filter and additional custom hierarchy columns but we may require to revisit once both are available since it is unclear if this solves all the use-cases. 
6. GROUP BY State -There has been requests to have group by process step and teams are using Group by State in the legacy roadmap. Need to understand if this is solved another way.

Suggestion: Review which groupings are planned, gather user feedback on missing options.