Multi-level navigation and easy menu definition

[mvlcek]

Yes it is a standard. But I need to show permanently a side-menu consisting of siblings belonging to 1 top lvl parent. This parent is set to not be shown in menu, and after reading for 5th time documentation I could only show all of its siblings as opened.

If the parent is not shown in the menu, then the children are also not shown in the menu (unless you use the flag I18N_SHOW_PAGES).
On the other hand, if the top page is in the (top) menu and you click on it, it is the active page and the code shown above will display all its children in the sidebar. If you click on one of the children, then its (sub)children are also shown, but not those of its siblings.
Do you have a link to an example so that I can better understand your problem?