In the spring, with healthy Japanese maples, bud-pinching is a common technique to keep internodes short on refined trees. It is a simple procedure, and needs to be performed about daily as Japanese maples are waking up in the spring.
The earlier you can identify the 2nd node and remove it, the shorter the internode will remain. In this example, I’ve waited about a day too long, but it helps illustrate the process.
Here is the extending new shoot:
Here is a markup showing the leaves in the 1st in blue, where to pinch out the second node in a yellow X, and the resulting length of the halted internode:
This tree is growing stronger on the top and left, and slower on the lower right, so careful attention will be required to keep up with the lower right side, as shown in the background below.
A couple weeks later, the maple is still growing, and I had a chance to pinch back more of the shoots.
The result is a lot of tips removed, and the profile is improved, but the density is still the same.
I will continue feeding, and in June, I’ll partly defoliate the tree to encourage back-budding. Meanwhile, I’ll keep a close eye out for wires starting to dig in.