Nonsense. It was only yesterday when I probably had over twenty, (spread across three machines and wishing I had more than four screens), and was accessing each one of them frequently.
Probably win+shift+x which toggles my main monitor input between my PC and my Switch so I can play Switch games without having to piss around with my monitor's shitty menus.
A more standard one: ctrl+r for recursive search in shell.
Ctrl - shift - esc for quick access to task manager and ctrl+win+c which swaps between colour or black and white in Windows 10. Come in quite handy at work that one when people hit it by mistake and have no idea how to change it back.
If you want to screw with people, on some Windows setups, right-side Ctrl-Shift can switch from left-to-right to right-to-left text - easy enough to do in front of them without them catching it, plus you have to use the left-side to undo it. :>
Win+x, u u to quickly shutdown Windows. Although I've done this lots of times and not realised Notepad was open and my laptop has been on in my bag all night (my work one stays on when the lid is closed).
Not a keyboard shortcut but you can customise Explorer so it defaults to starting at This PC.
Found this useful whilst currently working from home over a laggy RDP connection to my work desktop PC, where every mouse move is slow. The less mouse the better.