Airspeed limitations are some of the most visited references to flightsimmers or even real pilots. I normally seek for them in the aircraft’s manual or via Internet. For sure, the process doesn’t take a lot of work but it can be hardly called handy, especially when you need these information during a flight session.
Last week, I found out that there’s actually a quick way of locating these information in FSX and P3D quickly. I don’t know if you know it or not, but I was not aware of it in my 15+ years of flightsimming. How hilariously.
All we need is clicking on “Keyboard Assignments” under the drop-down menu of Help option. 
Then further choose “Reference”.
Certainly, not all default nor third-party aircraft provide these information. But it is not difficult to create our own reference for any aircraft we have, so that it can be accessed quickly when needed.
FSX TIMES 