Guys, I found a partial answer.
appdata = get(0,'ApplicationData')
hMainGui = getappdata(0,'hMainGui')
With that, I can see what is inside the application-defined data.
Also, with the handles command, I can see what is inside the handles struct.
With that, it is possible to clean some trash memory from my gui.
That is it for now.
Now the question is: how to make the gui faster and cleaner. Need best programming practices advices using GUI/GUIDE.