On the Windows app there is no right click menu on notebooks, only on notes, and it looks like it did before the upgrade. I just logged into the browser version, and the right click menu shows something completely different than the image above (image below). I would love to have a menu that looked like that.
I do see the New Stack option now, don't know how I overlooked it.
Not being able to drag notebooks around makes it so clunky. I'm reorganizing and I have to remove notebooks from existing stacks before I can put them in a new stack.
Related question: We can't have notes in the stack by themselves (not within another notebook). I thought for sure I was able to that before.