If this was mine I would plant in the ground for three years. I did this with one and it grew so fast it was incredible. The trunk is quite thin for the height of the tree, and a thicker trunk would make a big difference.I would let it grow unchecked, and then after about three years cut down hard. But it is your tree,
Since I'm really new to Bonsais, I don't feel that comfortable cutting major branches let alone trunk chopping a tree. For this Trident Maple, I just want to maintain its look and prune it to get more / fuller foliage. I plan to get some cheaper Bonsais to experiment with trunk chopping and pruning to get more comfortable working with Bonsais. Perhaps I should've started with a cheaper tree so I wouldn't feel as bad if I made mistakes. I saw a few cheap Bonsai plants at Rona and Home Depot which I may pick up this weekend to experiment.
Today I ended up cutting off a few branches towards the back of the tree that were intersecting, removing the small upward pointing branch, and removing the small sprout that was growing near the lowest branch on the left of the tree. I also wired two branches on the right side of the tree to get them to point more outwards so they wouldn't hit other branches; this also helped achieve a fuller looking tree. I'm pretty sure I didn't wire them correctly but it was a good learning experience since it was my first time. Now I'll have to research how to stimulate the tree to produce more foliage.
BTW, can anyone share any advice on how to deal with the branch in front circled in red? It's growing upwards and intersecting with a much larger branch. Should I try to wire it or simply cut it off? I've attached pictures of both the front and back of the tree. The two branches I've wired so far are circled in blue.