How to deactivate/reset the password login - like it was never used before?

A friend has a problem with his laptop. He likes to bring this device to me to check some things.
He has only the face recognition ("Hello") activated so far.

How can we together add an additional password login, just for the time as long as the device is under repair?
(I want to be sure that I can restart Windows 11 and login with his profile.)

How can I remove this password login possibility after I return the device to him?

(I know where I can set a new password.
But I can't find a way to disable this option after my help is finished.
He should only see his "Hello" login, no other option).

As far as I've determined with password and PIN log-ins they are part of the User Profile and only that User with the Face Recognition can work with it. If the same tech always works on the machine I'd create that User with its own password as Administrator which could simply be removed when no longer needed. Being restricted to the Face thing does make work difficult, was that the only choice available during setup? Usually one sets the User name and password, especially with a Microsoft Account then later assigns the PIN number.

As far as I know he did the setup itself and only has the face recocgnition activated ("because it was the easyiest way without remembering a code...")

My idea was: I additionally activate a password login just for the time I use it to repair. This would be not that difficult.
But how can I reverse such an activated password? The best thing would be, if I could give the device back, as if never a password option have been set.

Is this possible?

It can get complicated. I'd just have the logged-in user add another user with Admin rights which can be deleted later. And DON'T use the same User name as already there, make it at least one character different or completely different. Had to rebuild a computer because the owner added himself as a second User with same name and different password, it didn't create the new user folders in C:\Users so all the things he did were in the same folder as the original, couldn't easily separate.

I'm the only user of my PC but have a second Admin account set up ("test"). All my personal files are on an easily-removeable SSD so if it has to go in to the shop I can remove all my data.

Adding a new (local) account would be one way. Sure.
But if he has a problem inside his profile, I can't find and fix it without temporary login possibility to his profile.

The face has to be used to access the Profile, same as other logins, that's the downside of security.

Berton said:

The face has to be used to access the Profile, same as other logins, that's the downside of security.

Click to expand...

I'm not sure if understand it:
Does it mean that there is no way to add an additional way to login to the same profile if Helo-Face Recognition is already activated?

The issue probably lies in the Registry, 5 text files called Hives. It's what Windows uses to know how to run things and what portions it loads for different users.