How to manage local accounts on a windows office network?

You can use Group Policies to remove, add, set password etc. for local accounts as well.

However, this requires the machines in question to be added to Active Directory, which defeats the purpose of creating local accounts. In general, you should avoid any local accounts like the plague, and generally the Group Policies mentioned above are used just to remove and/or disable any local machine accounts in a AD environment.

Long story short, join all machines to AD and stop messing with local accounts.