I need such a diagram when I am playing a PC game using a Nintendo controller because they're the exact opposite of what the Xbox controller guide in the game will say. π¬
At least with a PlayStation controller, it only shares X as a face button and I am more likely to hit square on a PS game than the actual X on my controller when prompted to hit the Blue X on an Xbox because my X is green.
Was that as confusing to read as it was to write? Good.
If it makes it easier, you can tell steam to use the Xbox layout for whatever controller you use. My PS4 and 3rd party switch controllers are all "Xbox controllers" to steam so that I don't get confused.
That is the issue though. The Xbox layout is reverse to the Nintendo layout. So when it says press X in game for the xbox, it's actually Y on the Nintendo pad.
There is an option to reverse that specific to Nintendo controllers so that Y functions like X and B functions like A, though.
Honestly, it would be ideal if developers put all controller prompts in the game and had an option to set it to the one you want (even if you're not using that particular controller). I have played exactly one game that did this, and I don't even remember which one it was now. But I loved that option.
The controller that I'm using (Vader 3 pro) solves this for me. It uses the Xbox layout and also has a switch mode.
The trick is that in the switch mode, the face buttons are bound to their Xbox counterpart (e.g. A is B, X is Y, etc..) which makes following screen prompts much easier.