Judy, you've done very good work with this tree.
Now, let's step it up a notch!
You've cut back on it pretty well. I can't see it close up, but when doing the "hard" cut backs, it's best to cut back to a pair of "up/down" buds. You know how they alternate: side by side, then up/down, then side by side, the up/down, etc? If possible, choose an up/down set.
Then when they start to grow out, if the top one is growing, rub off the bottom one. Then, let the new twig grow out until there are 6 or 8 years pairs of leaves. Then, wire. Yes, wire the new soft shoots. The up bud will be growing up, but since it's young and pliable, you can bend it down so that its growing in the same direction as the branch. Yes, it will make a little hump. When you wire, wire out to the tip if you can, and put movement into the branch. Up, down, side to side. The little twigs are soft, you can put n a lot of soft movements in.
Oh, the leaves? Yeah, they're in the way, but wire around them. Use aluminum wire. It can be pretty thin, the branches bend easily.
Now, let it grow about a month. By this time, the branches will have set (lignified) where you wired them. The wire may even have cut in a bit. Remove the wire. The curves you put in have set.
Now, here comes the hard part: it's time to cut back!
How far? Remember the up/down, side by side stuff? Well, examine the part of the branch you wired, and cut back to the first up/down leaf pair!
Yes, this means you cut off 90 % of the branch, including most of all th branch you wired!
Do it all over.
Let it start to regrow. As soon as you see new growth, rub off the bottom shoot, just as before.
When it get to 6 or 8 pair of leaves, you guessed it, wire it again. Lots of movement.
Let grow. Remove wire when lignified. Cut back.
You might have to do three or four times over the summer.
This builds branches with movement, taper, and short internodes.
Tedious? You bet. Slow? Yes, indeed. But, it's the highest quality way to build trident branches.
Oh, and before someone says it, John Naka was wrong. In his book, he says to use the downward growing bud, not the top one. But that's wrong. In nature, the top bud would be the stronger one because it wold get all the light. The bottom one would eventually get sluffed off and that branch would die. If you go out and look at mature maple trees and their branches, as you follow the branch from the trunk out yo the tip, they have little humps. Little mountain ranges. They curve up, then down, then up and down, in a series of hills. Not: down then up, down then up. That would be a series of valleys. They don't do that.
Judy, I know you don't think I know anything about maples. Not so. I do. I just prefer conifers.
The technique I just described is how to build a great trident maple.