Does the property have the right not to seal the balcony?

Property has no right to enforce the law. You just need to seal the balcony with glass windows of the same color. The property may not agree with you. This is because laws and regulations can't be sealed, but he can't help it after you seal it. As long as your balcony is not too abrupt and beautiful, the property will not embarrass you with such a trivial matter. At least you're his master.