Q.magnolia tree
If I cut or trim a branch that is leaning low can I put this in water and sprout another root or plant another tree from the branch that has roots? Can I trim some low branches or just leave it? My tree is 30 feet tall and gets the nice white big flowers.

These articles will help you.
https://www.gardeningknowhow.com/ornamental/trees/magnolia/pruning-magnolia-trees.htm
https://www.gardeningknowhow.com/ornamental/trees/magnolia/propagating-magnolia-trees.htm