It seems that Home Assistant automatically shows a group if all of the entities in a given group are shown on a tab by other groups. That is a bit of a mouthful, hopefully this will clarify the issue I am experiencing.
The two pictures below shows what is displayed. In particular, note that the group “Outdoor Light Summary” is not defined in the group code above (neither is Hall Light Summary), but it is displayed on the frontend. My assumption is that this is because all the entities in the “Outdoor Light Summary” are shown in other groups (just the single group “Backyard Lights” at this point).
Depends how you have set it up I think, setup default view to control exactly what is shown and customize groups you don’t want shown with hidden: true in customize.yaml
Setting hidden:true in customize.yaml makes it so the group is never visible on any tab on the frontend. That hides the group globally which causes issues if you want that group to be visible on some tabs.