I’m able to add items directly under the Globals root name, but nothing can be done with them, so seems like a bug:
Yes, I’m aware you just select the Globals node and add them there.
Also, side note, you’re 3.5.1 notice did not contain a note to activate experimental mode, as I was not even able to access this and was confused until I found it. I’m sure less savvy people will be even more confused.