I think I’ve explained myself poorly, then.
Imagine that I have a page hierarchy like this:
Top link 1
–First sub level 1
—-Second sub level 1
——Third sub level 1
—-Second sub level 2
–First sub level 2
—-Second sub level 3
Top link 2
–First sub level 3
–First sub level 4
—-Second sub level 4
——Third sub level 2
——Third sub level 3
–First sub level 5
—-Second sub level 5
–First sub level 6
The top menu would list “Top link 1” and “Top link 2” (which is no problem to do using wp_list_pages())
If I were to click the “Top link 2”, the sidebar should show the following: (again, no problem with wp_list_pages)
First sub level 3
First sub level 4
First sub level 5
First sub level 6
Clicking “First sub level 4” should show
First sub level 3
First sub level 4
–Second sub level 4
First sub level 5
First sub level 6
Clicking “Second sub level 4” should show
First sub level 3
First sub level 4
–Second sub level 4
—-Third sub level 2
—-Third sub level 3
First sub level 5
First sub level 6
and so on.
Is this clearer?
What’s your idea? Are you thinking about hiding the irrelevant links? I tried that, but couldn’t get it right.