A course has one group of students
Course settnigs: Group mode: Visible, Force No
Group toggle icon is visible for activities and changes state (visually at least when clicked)
In either a new or existng assignment (probably others too) Group mode is No or Yes
There is no way to change the group mode other than select No or Yes. If Yes is selected there is no way of knowing if this is setting Visible or Seperate group mode for that activity.
Also just noticed that if Course settings are set to Sepaerate and Force=Yes, it is possible to select No for group mode in the activity settings. If one does this, the group mode icon on the course page still reflects the forced group mode setting for the course.