Can this navigation be done easily in WordPress?

Can anyone please let me know if a dual navigation style is easily achievable or not possible.
A WordPress developer I’m in touch with is telling me it’s not.

Basically, we would like the navigation to be via links at the top of the web page but also introduce a sub-navigation on the left side of the page.

So if you were on the HOME section, you’d have 3 tabs on the left, breaking HOME down into 3 sub parts.
If you clicked on another top link and went to section XYZ, the tabs on the left would vary to offer sub-sections of XYZ.

I know it can obviously be done from a HTML point of view but the guy is saying it’s not possible to do this and at the same time, keep the content editable within WordPress as Pages etc.

I would like all the main pages and their sub content editable via WordPress CMS.

Possible?
Thanks

ps: I would have added an attachment but not allowed as I’m a new user.

It is possible. Two options:

1. If the subpages are just children of the currently displayed page, you call:

    wp_list_pages( array ( 'child_of' => $GLOBALS['post']->ID ) );
   

   See Codex documentation. Very simple.

2. If you need a custom structure, for example a list of custom taxonomies when a special post type is viewed, you need to create a custom nav menu and a custom walker.

   The walker has to collect the associated items for the current page, save those somewhere and then another function would have to print it out where you need it.
   For someone not familiar with this stuff it may take a while to get this right. Our tag menus collects some useful information about this topic.