Switching Cards Around in Monopoly Deal 2
Looking at the rules here it says (emphasis mine)


  Each player can play up to 3 cards per turn. A play is considered any
  time a card is laid on the table (such as money into your bank,
  property cards on the table, action cards played into the middle,
  etc). You do not need to play all 3 cards per turn if you do not want
  to.


The same website in there strategy section here says


  It’s important to remember that you can re-arrange your monopoly cards
  on the table during your turn without sacrificing one of your three
  moves. This simple fact can help you maximize your income when
  charging other players.


You are allowed up to 3 'plays' a turn  this is defined as placing a card on the table.  moving a card from set to another is not one of you 3 'plays'