Although your posting is rather old, I'll hazard an answer.
I had the same problem. Are you also on OWB 11gR2 (18.104.22.168)? I'm sure they have changed the windows somewhere along an upgrade and forgot to change the documentation (which is abominable in general). According to me, Object Detail is now integrated in Property Inspector, and Expert Explorer is, as you guessed, integrated in Structure. In Structure you can fiddle around with variables and parameters.