I think George / Leader should explain this.
I agree that today it makes no sense looking for a nsb folder which is no more to be seen within the project folder.
Months or years ago a nsb folder was built within each project folder. There were always and still are warnings that one should not put own files into nsb folder.
So one can imagine they do not want you to do anything with the nsb folder.
In recent times my app folders do not contain (visible?) nsb folders any more. There is not yet any explanation about this change.
I had a problem comparable with yours. That’s when I noticed that the nsb folder is no more available or visible within the project folder.
One can find this folder nsb within the app’s folder following the path you indicated (Preferences menu) at your server when you already deployed with F6.
PS: You can find NSB folder as well when you run your app (F5) and open the Chrome debugger (F12 within Chrome). See attached screenshot.