This is to create a user that does not show in Control Panel → User Accounts or on the Sign In Screen
At an Administrative Command Prompt
net user UserName PassWord /add (hit enter)
net localgroup Administrators UserName /add (hit enter)
UserName and PassWord are replaced with your chosen values
https://www.windowscentral.com/how-hide-specific-user-accounts-sign-screen-windows-10
At an Administrative Command Prompt
wmic UserAccount where name='UserName' set PassWordExpires=false (hit enter)
Replace UserName with the user account you want to hide.