How much customization can you do with custom admin bar plugin?

I’ve been trying out the custom admin bar plugin and it seems to me that you can’t customize the admin bar to the extent that is done on, correct?

It seems that 1. you can change the WordPress logo and 2. add additional submenus (links) under that menu, 3. remove existing WordPress menus already in the bar.

But you can’t add any additional menus, so where would I start to do that? (I did a search of the forum under “custom admin bar” but didn’t see anything.