To create a hidden user or to hide a user from showing in the welcome screen, just perform this registry edit.

1. Run regedit
2. Navigate to the following key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList
3. Create new DWORD value with string as exact username (to be hidden) with value "1".

Now you can not able see the user in the welcome screen.

To revert back just delete the create key or set the value as "0".

To login the hidden user, log-off the current user and press CTRL+ALT+DEL twice. Now you can find the input field to specify username and password. Specify the hidden username and password to login.