Question
3 years ago planted some type of purple maple, curb/grass area next to sidewalk. Now main tree with a number of branches is about 10', but the leader is another 6' above that with just a few shoots coming out, with no other branch formations growing. Do I trim the leader? If so where do I trim it?

Answer
No this is the main terminal of the tree and pruning it may damage the tree. The main terminal is the part of the tree that gives the tree height and is the fastest growing part. It normally will grow tall and then produce side branches. Sounds normal to me.