That's not what Planck's Constant is. Planck's Constant connects energy to length (in space or time). It's just a way of shifting units around.

You're thinking of the Planck Length, which is the result of combining the Planck Constant with the speed of light. It also happens to be the wavelength of a photon so short that its energy makes it a black hole, connecting it to gravity.

It's often presented as if it were the fundamental unit of length, but that's a guess at best. There's no specific reason to believe it, other than the fact that it happens to be a way to connect length, charge, and gravity. That's evocative, but hardly proof. There's neither evidence for it nor a well-supported theory behind it.