Solved! Go to Solution.
I didn't actually try the "Display value", maybe is something as an alias for the key, idk. You also can't create a key, delete it and then create it again. Since an error will show that the key already exists. That is when i understood the meaningn of the fiel. Sadly it take me 3 session properties to understand it. It's a nice really addtion. Hope it reaches the Mobile app also.