I wonder what possible benefit Graphisoft imagined would derive from having a sub-menu after clicking on "Open"?
Surely the 2 other options, and the "recent projects" list, could have been incorporated in the one menu.
I would really like to have "Open a New Instance of Archicad" on this menu, then I could see a use for a sub-menu, because now we could have the option to "Browse" or to select from the "recent projects" list in either case.
This may seem trivial, but I think there is some psychological block (and not just me!), when browsing for a file via the system dialog, that makes you forget to tick the "Open a New Instance..." box. So then you get "Save the drawing?" and you realise your mistake and go round again. (Sigh!)
I notice that there is now an option (since version 15) to force a new instance of Archicad by default whenever opening a drawing picked from the 'Recent Projects List' (or when clicking on a file in 'Finder'). It's under 'Work Environment / More Options'.
This kind of goes half way to solving to the problem. I suspect it will result in my having more versions running at one time than I really want!