Variables are managed directly within the AutomationView views.
Using the User Interface (Button):
Click the Variables icon in the Activity Bar (the far-left sidebar) to open the Variables view. This view automatically populates with variables from your .machine and .seq files. Inside the view's top title bar, you will find buttons to toggle viewing modes:
Using the Command Palette:
It is also possible to manage them via the Command Palette:
Ctrl+Shift+P / Cmd+Shift+P).