Jumping should be discouraged as luxating patella can occur spontaneously and affects toy breeds. I have foam steps from
www.petstairz.com and love them. A member here, Diannet, now sells some wood ones as well.
Mine every now and then will seem to want to jump (like if a prized possession goes flying off the bed and they want to dive for it) and I have been there to say "Use your Stairs" and they do. I clicker trained my dogs to use stairs, and it was very easy. Even Teddy learned it quickly, although sometimes he rests on the stairs in between using them, or hangs out on them and has to be redirected.
Definitely time for stairs/ramp so this jumping comes to a halt, it is really quite dangerous for a yorkie.