Nothing in the Income Withholding for Child Support Act shall be construed as prohibiting a person from consenting to an income withholding order as part of a property settlement agreement incorporated into a decree dissolving a marriage or by agreement in a proceeding in the county court, district court, county court sitting as a juvenile court, or separate juvenile court in which the payment of child, spousal, or medical support is an issue. Any such order or agreement shall be filed with the clerk of the district court who shall notify the person's employer or other payor, if any, of the order or agreement by first-class mail and file a record of such mailing in the court. The income withholding shall be treated in all other respects the same as an income withholding initiated pursuant to section 43-1720.