In 1972 Knud was still alive and would in case of a remaining salic law have succeeded his brother as Christian XI. He died in 1976. At that time there are several options:
1 the marriages of Knud's sons are deemed dynastic and they return in line of succession so we would have King Frederik X succeeding his father in 1976 and being the current monarch.
1a the Salic law was altered in the 1980's/1990's or 2000's and his niece Josephine would be the heiress apparent.
1b the Salic law remains and either Constantine of Greece or one of his sons or grandsons would accept to be the heir to the Danish throne. Constantine never formally abdicated so i expect it would have to be one of his sons or grandsons. Assuming he outlives his wife's first cousin.
2 the marriages of Knud's sons are not deemed equal but between 1972 and 1976 the line of succession is opened to female succession. In that case princess Elisabeth would have succeeded in 1976 and we really cannot tell who would have succeeded her. Her niece might be one option, another her cousin Margrethe and even the Greek line comes into play.
3 the Salic laws remain to this day, than either Constantine or one of his sons could have succeeded in 1976 because by that time Greece was a Republic.