Dropping this here (sorry it has been posted before), taking it from how maya does it, which I have always found useful on big scenes:
|Expand or collapse the level under a node.|Click the plus 
or minus 
next to the node name.|
| — | — | — |
|Expand or collapse all levels under a node (quick way to see all nodes).|Shift + click the plus or minus next to the node name.|
The basic idea is that if you open or close a hierarchy of the outliner while keeping Shift pressed, it’ll collapse or expand all the child.
Of course, without Shift, simply expand and collapse retaining the previous settings.
My2c.
L.