When I go to hide a group it works, but when I go to “show only selected”, in the right click > visibility menu, the operation I expect does not work, and the group is hidden also, when I specifically selected it so it would not be hidden.
After some investigation I found that when I click on a group in the level editor the group actor in the Would Outliner does not show as selected. When I click on the group actor inside of the World Outliner it selects the group also in the level editor, hence the odd title that I think when you select a group it does not select the group actor in the World Outliner, hence why I think that this is a 1 way selection process.