If you are linked to an online account - you must have a password.
You can create a use a PIN number so you can just type in numbers from the number key pad. I use that at home for quicker log ins. Even for a local account w/ a password you can create a PIN. Also - even if you use the same WindowsID to log into your Win10 - each device can have a different local PIN number.
I think the only way to not have a password is to create and use a local account for logging in. If you use a local account that already has a password - you can't "update" it to a null password.