Everybody knows shortcuts save time. Almost nobody learns new ones, because the moment you need one you are mid-task, and looking it up costs more than the slow way.
That is a memory problem, and the fix is physical.
Twenty, not two hundred
Every shortcut list on the internet is exhaustive, which makes it useless — you cannot learn from a reference, only look things up in one. These cards each carry twenty, chosen for how much time they save multiplied by how often you would use them. Learn a card in a fortnight and turn it over.
Why printed
A reference on your screen competes with the work on your screen. A card standing under the monitor is in your eyeline while your hands stay where they are, which is the only reason a glance is cheaper than a search.
Both key sets, always
Windows and Mac columns on every card. Most desks are mixed now, and a reference card that is wrong for the machine in front of you is just clutter.