Re: Adding menu items to the admin bar
Oops, I had removed the page IDs from the plugin file, but the file I uploaded to pastebin was the one that has my page ID exclusions.
Nice touch with the pageLinkDropdown idea! I take your hint and I’ll see if, following your example, I can figure out how to add that option to wp_nav_menus. 
I fully agree that the user should be able to control values and parameters. Next challenge then is to learn how to create (and code) an admin area to give users that control. Here’s the start of my study program: https://codex.wordpress.org/Creating_Options_Pages and https://codex.wordpress.org/Adding_Administration_Menus
Oh goody… more fun! 
