Thank you for the reply. I know I can set a custom cursor.
Input.CursorShape.CURSOR_WAIT implies to me there is already a built-in cursor shape for "input wait mode".
See https://docs.godotengine.org/en/stable/classes/class_input.html
I can get the current cursor shape by calling Input.getcurrentcusorshape(), I can set the default cursor shape by calling Input.setdefaultcursorshape (cursor_shape).
There just doesn't seem to be a way to set the current cursor shape using the Input.CursorShape enum values.