When a group is collapsed, you can use the Select Shot menu item to add shots to the selection list. This menu item also helps you determine which shots in a collapsed group are selected. Selecting shots in a collapsed group is useful for example if you want to remove shots from a group.
A drop-down menu appears containing the names of all the shots in the group. Each entry has a toggle which is checked if the corresponding shot is currently on the selection list. By choosing a shot, you toggle it on and off the selection list.