Rotate turns the selected groups and components by exactly 90° about one world axis. The pivot is the center of the selection's combined bounding box. Loose faces and edges are ignored. You cannot type an angle.
Hold Shift while you click to turn counter-clockwise. The box under the cursor is drawn heavier. After each turn the three boxes are rebuilt. The tool stays open.
With nothing selected there are no boxes. The status line tells you to select groups or components and start the tool again. Selecting more while the tool is open is not picked up until a turn succeeds or you start the tool again.
The same 90° turn, without clicking a box:
Hold Shift with the arrow to turn counter-clockwise.
Ctrl toggles (press once). While it is on, a green + sits by the cursor. The next turn spins the original and leaves an unrotated copy where it was.
Each turn is one undo step, named like Rotate 90° X (or Y, or Z), with (copy) when Ctrl is on.
There is no VCB. Tab and Alt are not used.