Please give us the freedom to remove the code and not create guarded blocks. I have often the problem, that I want to remove code, that I accidentally added via the GUI designer like double clicking the button (I always think that I can change the label on it, no it will create an action listener for it). IntelliJ doesn't do that and I guess the JFormDesigner will not do this too.
So please don't say, you are not allowed to change the code. There are some others, when you google for it, that they have also the same problem. We are developer, we should know, what we are doing.
Customize Code will also not help to 100%. There is no reason to make such generated code read only. Often I have to open the file in VS Code for example, to remove the unused code which is not nice.