Custom WordPress Navigation Menu

I have a WordPress site with a vertical navigation menu - [login to view URL] - and each of the navigation menu items that corresponds to a project has one or more sub pages or a blog category that I want to link to. When the visitor clicks on the main project link, I want associated/sub pages and blog category links to display as block items below the link, and for the original link to have a special CSS class to communicate what project is being viewed. I think this is going to require PHP URL query matches, and I envision the main project pages having a section in the page editor in which sublinks can be defined, which become the block links below the main project link. I am open to suggestions, whatever is cleanest, efficient, and works. See two attached screenshots for visuals.