[CONNECT] Screen Menus - opening one from another without dismissing the first?

I'm looking at screen menus to replicate the old Main Classic Toolbox.Tasks were strange enough; the Ribbon is going to make my head explode. I want my Main Classic toolbar, and I'm trying to make it happen.

What I don't understand entirely is how secondary menus are activated. From this blog it looks as if I can just create saved views for each submenu if they are placed on different levels.
I also see in the Help file, a sentence about submenus:

Sometimes it is useful for a screen menu to open another screen menu while remaining active itself. The SCREENMENU OPENSUBPOPUP key-in is used for that purpose.

If I am trying to emulate the Main Classic Toolbox, where I click to get a flyout of each associated toolbox, is that better organized as saved views, or as a subpopup?

I intend to have the screen menu open in its own window so I can keep it up all the time.

Thank you.