Re: Cannot overwrite remote file '/etc/nginx/nginx.conf'. Press 'Delete' to delete the file and create n
Please explain why you believe it's WinSCP problem. It looks like you simply do not have permissions to edit the file. You possibly need to login with another account (or even root) to edit it.
See How do I change user after login (e.g. su root)?
See How do I change user after login (e.g. su root)?