Since the introduction of Planner in Office 365, the evolution of this tool / solution has been very slow compared to other services and solutions we have in the platform. Therefore, from time to time we have some small pieces of new functionality added to Planner such as the recent ability to add more than one Planner Plan to an Office 365 Group directly in the Planner App (This was already possible in Microsoft Teams and in a modern SharePoint Online Site):
Once you clic the “Create” button, you will see in the “New Plan” window the regular options to create a Plan and also a new “Add to an existing Office 365 group” link.
This link allows you to choose an existing Office 365 Group, so when you go back to the “New Plan” window the Group is shown there and you can proceed to create the Planner Plan.
As the Plan is added to an existing Group, Group Name and Group Members are automatically presented in the Planner user interface: