There
is a thread where it is discussed whether it’s possible to shuffle decks like these.
When the rules tell you to shuffle a deck with just one card it’s obvious what you should do (nothing, or maybe take it up and put it down again after assuring yourself that it is indeed just one card). So the question is not on what you should do, but how to describe what you did. Did you shuffle? Or did you try to shuffle, but failed?
How can it matter? Because of the lose track rule. See the original thread.
There is no official ruling on this yet, and when people expressed different opinions Donald wrote that he is happy to continue gathering data. I have avoided writing a “me too” comment, and others might have done that as well, so here is a chance for us to vote instead, where maybe more people will show how they interpret this.