Hi there,
I think you will find that the Transition Altitude on descent in the MCDU, defaults to what it is on climb. On the 320's I fly the Trans Level is then correctly loaded, when the STAR is selected. If operating to a port without STAR's, I am in the practice of entering the appropriate Trans Level.
What do you mean "discouraged"? It's not something I have ever come across?
Hope that helps a little...