Configuring a Plesk website as a reverse proxy for the control panel

Login to Plesk
Select your domain
Select Apache & nginx Settings
Uncheck "Proxy mode"
Click on Apply (this is important before continuing)
Set "Additional nginx directives" to the following. Replace x.x.x.x:8881 with your control panel's IP and secure port.

location / {
	proxy_pass https://x.x.x.x:8881;
	proxy_redirect off;
	proxy_set_header Host $host;
	proxy_set_header X-Real-IP $remote_addr;
	proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
	proxy_set_header X-Forwarded-Host $server_name;
	client_max_body_size 0;
	proxy_http_version 1.1;
	proxy_request_buffering off;
	proxy_buffering                 off;
}

If "Last login" shows the incorrect IP

Go to servers > master > website settings.
Set "Web Proxy IP" to the IP that is shown.
Set "Web Proxy IP Header" to "X-Real-IP".
Save and select Tools > Restart monitor.
After the control panel has been restarted you need to log out and log in twice so it shows your real IP.