The beta build 21390 introduced new changes to the Sanctuary Map navigation UI (User Interface).
I created an Adventure-Mode game. As I opened the Map by pressing (M) on the keyboard, I noticed the navigation UI was changed slightly.
Before the patch, you would click a small globe with a curved arrow on the upper-left corner of the map to jump from your current Act/Region to the global map of Sanctuary -- where you could then select another Act/Region (Act I-to-V) to jump into.
In this version of the beta client, however, that globe icon UI was replaced by an horizontal bar named "Map Level". This bar contains only three radial buttons. Each side of the horizontal bar has a button to toggle through these radial buttons (+) and (-).
This Map Level toggle UI is very buggy at the moment and still in development/progress. The + and - buttons are not working at all at the moment. You can only click the first radial button when you are within an Act, which takes you back to the Global Map of Sanctuary. You can't click the radial buttons when within the Map of Sanctuary.
The logic of what each radial button represents:
Radial Button 1 = Map of Sanctuary
Radial button 2 = Specific Act/Region
Radial button 3 = Your current location's map (the one when you press the TAB button)