Player A has A,2,Q,K. Board cards are 3,4,6,K,Q. Can he or she win low with a A,2,3,4,6? Change cards for hi and win hi A,Q Q,K,K?
Yes, a player can use any combination of two cards from their hand and 3 from the board in Omaha Hi-low to make a complete hand, and they do now have to be the same cards for the high and low hands.
In your example for the high hand, it would actually be KKQQ6.