Can I add insulation to the top of my oven range (under the drip pans)
Maybe with a sheet of aluminum on top of it to prevent drippings from saturating the insulation (which would cause a fire hazard)  However, you could cause the top steel of the oven to overheat and damage the finish.  And if a fire started and burned the house down if they discover the oven was modified your homeowners insurance may not pay out.  There are all kinds of liability risks to modifying a power appliance.  Since this is a cheap electric oven you can get a much better one for not much money used off craigslist.
However, we have a pretty expensive range ourselves my wife has melted plastic by accident on top of it.  I just handed her a razor blade scraper and told her plastic and cooking do not mix.  It only happened once. :-)