Size Scroll Bar in source Add Data

[#1]

Description - When adding data to a dataflow, on tha Select Data Step, when we Uploade a Json that is bigger than what the first seen screen can hold, there is no scroll bar to look/verify the rest of the json. 

Why is this feature important to you - Because it supposed to be there, is more like a bug than a improvement. 

How would you like the feature to work - It must have a scrool bar, that simple. 

Current Behaviour - There is no scrool bar.