Thanks Harky. I think the first Sierra CD game was actually Mixed-Up Mother Goose, not KQ5.
As for your list, I think that the copy protection was taken out for the CD release of SQ4. And the plug adapter you mentioned, I don’t think that’s found in the manual, I think you’re supposed to figure it out yourself in the game (because you can still return to the arcade and from there to Radio Shack after you see the plug connectors in Vohaul’s palace).
I think some of the SQ4 manuals told the correct coordinates for making the laser beams horizontal, but it was more of a spoiler than a copy protection thing, because it was possible to figure it out without the manual (I think 🙂 ).
As for LSL5, it does have copy protection, but while it was released on a CD, it was just the floppy version shoved on a CD-ROM, not a real CD version, so it doesn’t count.