In the meantime I wasn't able to understand why the json based code doesn't work, but was able to solve the sorting the following way:
ButtonAdd onClick & not TextBox is ""
- Array Push back TextBox.Text on X axis
- Array Sort X axis
-- Array For each X element
--- Array Current value =/= 0 List Add Item Array.CurValue
Also in the Array property menu the dimension of the array has to be set to 1 on each dimension: Width=1, Height=1, Depth=1 otherwise this doesnt work.
Note that I had to set the condition Array Current value =/= 0, otherwise an empty line would appear in the listbox. This is because the array is prefilled with a first value of zero, because i had to set Width to 1, for the array to receive add values.
It works, but since i am always interested in learning new techniques, any ideas how to do this better would be much appreciated.