Re Egret and Command-Power, I’m pretty sure the key combination (and the command-control-power hard reset combo) is always active, and not a Macsbug thing. ISTR you can trigger sad Macs on boot with it, which would be before Macsbug is loaded (I think), and also access the mini debugger if Macsbug isn’t loaded. At least from what I remember about my old LCII (would have to dig it out to double check though).