1) Track View shows that an object is a child of another by default.
2) Select By Name dialog has the option to show hierarchies
3) Schematic View shows it, too
4) One can navigate the hierarchy using PgUp and PgDn, so when I suspect an object has a parent, I just hit PgUp to see who is there...
5) Finally, in the display properties, there is a Link Display rollout where you can enable visual representation of linked objects so you can see who is linked to whom in the viewports...