OK, Throttle (Right or Left) OFF/IDLE does actually work, it's just not obvious how you go from IDLE cutoff into idle when cranking the APU past 20%. I thought you'd start from the cutoff position because (theoretically) that's where you left the power levers when you last shut down. It turns out that in order to actuate the IDLE command, it's actually easier to start with the power lever forward of the cutoff position, then pull it aft into the cutoff position, THEN move it forward to IDLE and that engine will then spool up to idle normally. As long as I don't have to touch the keyboard, that's good enough..