In the Mother of All Demos[1], Engelbart's 5-key contraption is a "chorded keyboard," an idea that resurfaces from time to time.
Engelbart also talked about UI for trained adults vs the kind of GUI we are used to today, designed for children. The difference in design based on intended use both in the mechanical inputs and in the display are incredibly important. One would hope that similar ideas shape designs today.<p>There is no mention of PLATO[2] whatsoever.<p>And I stopped scanning. Maybe this is intended as a "personal history" of GUIs, but otherwise, it's lacking.<p>[1] <a href="https://invention.si.edu/mother-all-demos" rel="nofollow">https://invention.si.edu/mother-all-demos</a><p>[2] <a href="https://en.wikipedia.org/wiki/PLATO_(computer_system)" rel="nofollow">https://en.wikipedia.org/wiki/PLATO_(computer_system)</a>