Selecting objects that are grouped together in the viewport will not highlight the group actor in the World Outliner. One known result of this is, after selecting the group in the viewport, right-clicking and choosing "Show Only Selected" results in the group not being visible at all.
*See attached image
1. Open Blank Project with Starter Content Only showing two chairs and table map
2. Group table, chairs and statue
3. In world outliner, search "group" so this group is the only thing listed
4. Select the group form the Viewport (not Outliner)
5. NOTE: Group is not highlighted in the outliner
6. In the viewport, rmb click and select "Show Only Selected"
RESULT: Everything in map becomes invisible, including the selected group, which is not selected in the World Outliner
EXPECTED: The selected group to be the only thing visible AND to be highlighted as selected in the World Outliner
Head over to the existing Questions & Answers thread and let us know what's up.