The bottom line is that we don’t know. Most recent studies seem to indicate that single short exposures to anesthesia are not harmful to the child.
My general advice is that it’s unwise to perform any truly elective anesthesia on a child. Make sure that your child really needs to have a procedure, and whether they need anesthesia for it.
Fortunately, it’s a rare thing to do ‘elective’ procedures under anesthesia on children...though we do see them every now and then.